Methods of etching conductive features, and related devices and systems

ABSTRACT

A method of making a device patterned with one or more electrically conductive features includes depositing a conductive material layer over an electrically insulating surface of a substrate, depositing an anti-corrosive material layer over the conductive material layer, and depositing an etch-resist material layer over the anti-corrosive material layer. The etch-resist material layer may be deposited over the anti-corrosive material layer, and the anti-corrosive material layer forming a bi-component etch mask in a pattern resulting in covered portions of the conductive material layer and exposed portions of the conductive material layer, the covered portions being positioned at locations corresponding to one or more conductive features of the device. A wet-etch process is performed to remove the exposed portions of the conductive material layer from the electrically insulating substrate, and the bi-component etch mask is removed to expose the remaining conductive material. Systems and devices relate to devices with patterned features.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. ProvisionalApplication No. 62/432,710, entitled “METHOD OF ETCHING CONDUCTIVELINES,” filed on Dec. 12, 2016, which is incorporated by referenceherein in its entirety.

INTRODUCTION

Manufacturing of a variety of electronic devices and electroniccomponents requires the fabrication of patterned layers on a substrate.For example, microchips, printed circuit boards, solar cells, electronicdisplays (such as liquid crystal displays, organic light emitting diodedisplays, and quantum dot electroluminescent displays), and a variety ofother electrical or optical devices and components, may be comprised ofmultiple overlapping patterned layers of different materials supportedby a substrate. Manufacturing one such patterned layer on a substratemay be carried out by applying an unpatterned layer of material onto thesubstrate, preparing on such layer an etch resist mask, and performingan etching process to remove the portions of the layer that are notcovered by the etch resist mask, thus forming the patterned layer on thesubstrate.

In one illustrative example, which can be used for manufacturing of, forexample, printed circuit boards (PCB's) or other electronic components,an electrically conductive metal layer is applied to an electricallyinsulating surface of a substrate (or equivalently, an electricallyconductive layer is formed on an electrically insulating surface of asubstrate), an etch resist mask is applied to (or formed on) theconductive layer, and an etching process is performed to remove portionsof the conductive layer that are not covered by the etch resist mask,thus forming a patterned conductive layer on the electrically insulatingsurface of the substrate. The patterned conductive layer so formed maycomprise one or more conductive features further comprising, forexample, lines, circles, squares, and other shapes, of conductivematerial on the electrically insulating surface of the substrate. Incertain cases, the etch process used to form such a patterned conductivelayer may be a wet etch process, whereby a liquid etch materialinteracts with the conductive layer so as to remove the conductive layerfrom the electrically insulating surface of the substrate. Such a wetetch process may be a wet “chemical” etch process, for example.

A frequent characteristic of wet etching is “undercutting”, which, inthe representative example of etching a conductive layer, refers to thephenomenon of removal of conductive layer material under the etch mask.Such undercutting may decrease the conductivity of the conductive layerby reducing the feature width in the direction perpendicular to the flowof electrical current relative to the corresponding width of the etchmask. As a result, the conductivity may fall below a desired level. Sucha reduction in conductivity due to undercutting may be especiallypronounced in the case of relatively small feature widths, for example,feature widths below about 60 This undercutting phenomenon may alsoimpart to the conductive features sloped or non-planar “side-walls.” Asused herein, “side-walls” refers to lateral surfaces of a feature, suchas the walls on the sides of the features which extend down from the topof the feature adjacent to the etch mask to the bottom of the featureadjacent to the substrate. In some cases, a feature associated with suchundercutting may have sloped or non-planar side-walls such that a widthnear the top of the feature (near to the etch mask) is smaller than awidth at the bottom of the feature (near to the substrate). As a certainminimum feature width at the top of the feature may be desired, forexample, to achieve a desired conductivity or to achieve a desiredelectrical frequency response, such undercutting may impose lower limitson at least one of the minimum feature width or the minimumfeature-to-feature spacing, thereby limiting the density of featuresthat can be provided on the substrate.

Undercutting may be undesirable for applications other than thepatterning of conductive metal lines in the manufacture of PCBs. Forexample, similar considerations as described above for PCB's may alsoapply to other applications utilizing metal lines for the purpose ofcarrying electrical current and/or electrical signals, for example, inthe manufacture of microchips, electronic displays, or solar cells. Inanother example, other considerations may apply to applicationsutilizing a patterned layer a non-metal, for example, an optical coatingor an insulating layer, in the manufacture of an electronic or opticaldevice or component, where substantially vertical side-walls aredesirable.

A need exists for improved techniques that mitigate (e.g., reduce oreliminate) undercutting on features formed using a wet etch process whenforming patterned layers on a substrate for the purpose of manufacturingelectronic and/or optical devices or electronic and/or opticalcomponents.

In conventional processing, the etch mask described above is formed byapplying to the substrate a blanket coating of a photo-sensitivematerial (often a UV light sensitive material) that upon pattern-wiselight exposure and subsequent processing is converted into the etchmask. Such subsequent processing typically includes removal of thephoto-sensitive material (e.g. during a developing step) so as to formthe etch mask pattern on the substrate. In many instances, for examplewithout limitation, when using an etch mask to pattern a metal layer ofa PCB, the etch mask covers less than 50% of the substrate surface andthe removed photo-sensitive material is discarded as waste. In manyinstances, the removal of the photo-sensitive material requires washingthe substrate in a liquid (e.g. a developer) and the liquid used toperform such washing is discarded as waste. In many instances, forexample without limitation, when using an etch mask to pattern a metallayer of a PCB, the photo-sensitive material is prepared on a carriersheet and is then transferred from the carrier sheet onto the substratevia lamination, and after such transfer the carrier sheet is discardedas waste. When manufacturing electronic and/or optical devices and/orcomponents, it is often desirable to reduce waste. One approach toreducing such waste is to directly apply the etch mask onto thesubstrate in the desired pattern using non-impact printing (e.g. inkjetprinting) to deliver to the substrate a liquid etch mask ink in thedesired pattern and then subsequently process the liquid coating (e.g.via drying and/or baking) to form the finished etch mask. However, theinks delivered by such non-impact printing methods typically are notwell absorbed on the surface of a substrate used in the manufacture ofan optical and/or electrical component and/device, and such inks mayspread and/or translate on such a surface in an uncontrolled way,leading to such phenomena as clustering, coalescence, and dot gain. As aresult, the etch mask resulting from such non-impact printing processesmay exhibit reduced resolution, lack of details, inconsistent patternedline width, poor line edge smoothness, connections between features thatare to be separated, and breaks in features that are to be continuous.

In such cases that non-impact printing is utilized to prepare an etchmask as described above, a need exists to mitigate (e.g. reduce oreliminate) such uncontrolled spreading and/or translation of thedeposited liquid etch mask ink on the surface of the substrate.

SUMMARY

In one exemplary aspect of the disclosure, a method of making a devicepatterned with one or more electrically conductive features includesdepositing a conductive material layer over an electrically insulatingsurface of a substrate, depositing an anti-corrosive material layer overthe conductive material layer, and depositing an etch-resist materiallayer over the anti-corrosive material layer. The depositing anetch-resist material layer over the anti-corrosive material layer, theetch-resist material layer and the anti-corrosive material layer forminga bi-component etch mask in a pattern resulting in covered portions ofthe conductive material layer and exposed portions of the conductivematerial layer, the covered portions being positioned at locationscorresponding to one or more conductive features of the device. Awet-etch process is performed to remove the exposed portions of theelectrically insulating substrate, and the bi-component etch mask isremoved to expose the remaining conductive material of the coveredportions of the conductive material layer, thereby forming the one ormore electrically conductive features of the device.

In another exemplary aspect of the disclosure, an apparatus for making adevice patterned with electrically conductive features includes a firstdeposition module configured to deposit an anti-corrosive material layerover a conductive material layer over an electrically insulating surfaceof a substrate, a second deposition module configured to deposit anetch-resist material layer over the anti-corrosive material, and a wetetching module configured to etch the conductive material layer of thesubstrate.

In yet another exemplary aspect of the disclosure, a device patternedwith electrically conductive features comprises a substrate having anelectrically insulating surface and a conductive feature disposed on theelectrically insulating surface. The conductive feature comprises aheight (c) measured in a direction normal to the electrically insulatingsurface, a first width (a) measured at the electrically insulatingsurface, and a second width (b) measured at an end of the conductivefeature opposite the electrically insulating surface along the height(c) of the conductive feature. A value of half a difference between thefirst width (a) and the second width (b) divided by the height (c) is atleast 2 (i.e. [a−b]/c≥2).

In yet another exemplary aspect of the disclosure, a method includesapplying a first liquid composition comprising a first reactivecomponent onto a metallic surface to form a primer layer, and image-wiseprinting by a non-impact printing process on the primer layer a secondliquid composition comprising a second reactive component to produce anetch mask according to a predetermined pattern. When droplets of thesecond liquid composition contact the primer layer, the second reactivecomponent undergoes a chemical reaction with the first reactivecomponent to immobilize the droplets.

Additional objects, features, and/or other advantages will be set forthin part in the description which follows, and in part will be obviousfrom the description, or may be learned by practice of the presentdisclosure and/or claims. At least some of these objects and advantagesmay be realized and attained by the elements and combinationsparticularly pointed out in the appended claims.

Both the foregoing general description and the following detaileddescription are exemplary and explanatory only and are not restrictiveof the claims; rather the claims should be entitled to their fullbreadth of scope, including equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D show cross-sectional and plan views of a device undergoing aconventional process for forming a patterned layer on a substrate.

FIGS. 2A-2C show cross-sectional and plan views of a device undergoinganother conventional process for forming a patterned layer on asubstrate.

FIGS. 3A and 3B show cross-sectional and plan views of a deviceundergoing another conventional process for forming a patterned layer ona substrate.

FIGS. 4A-4C show cross-sectional and plan views of a device undergoinganother conventional process for forming a patterned layer on asubstrate.

FIGS. 5A-5C show cross-sectional, plan, and perspective views of adevice undergoing another conventional process for forming a patternedlayer on a substrate.

FIGS. 6A-6D show cross-sectional and plan views of a device undergoing aprocess for forming a patterned layer on a substrate according to anexemplary embodiment of the present disclosure.

FIGS. 7A-7C show cross-sectional and plan views of a device undergoing aprocess for forming a patterned layer on a substrate according toanother exemplary embodiment of the present disclosure.

FIGS. 8A-8D show cross-sectional views of a device undergoing a processfor forming a patterned layer on a substrate according to anotherexemplary embodiment of the present disclosure.

FIGS. 9A-9C show cross-sectional views of a device undergoing a processfor forming a patterned layer on a substrate according to anotherexemplary embodiment of the present disclosure.

FIG. 10 shows a cross-sectional view of a device during processing toform a patterned layer on a substrate according to a conventionalprocess.

FIG. 11 shows a cross-sectional view of a device during processing toform a patterned layer on a substrate according to an exemplaryembodiment of the present disclosure.

FIG. 12A is a cross-sectional view of a device during processing to forma patterned layer on a substrate according to an exemplary embodiment ofthe present disclosure.

FIG. 12B is an enlarged view of the portion in circle 12B of FIG. 12A.

FIG. 13A is a cross-sectional view of a device during processing to forma patterned layer on a substrate according to another exemplaryembodiment of the present disclosure.

FIGS. 13B and 13C are enlarged views of the portion in circle 13B,C ofFIG. 13A showing characterizations of different states in B and C.

FIG. 14 is a flow chart showing a work flow for forming a patternedlayer on a substrate according to an exemplary embodiment of thedisclosure.

FIG. 15 is a flow chart showing a work flow for forming a patternedlayer on a substrate according to another exemplary embodiment of thedisclosure.

FIG. 16 is a flow chart showing a work flow for forming a patternedlayer on a substrate according to another exemplary embodiment of thedisclosure.

FIG. 17 is a flow chart showing a work flow for forming a patternedcopper layer on a substrate, as, for example, in the manufacture of aPCB, according to another exemplary embodiment of the disclosure.

FIG. 18 is a block diagram of components of a system for forming adevice according to various exemplary embodiments of the disclosure.

FIG. 19 is a flow chart showing a work flow for forming a patternedlayer on a substrate according to another exemplary embodiment of thedisclosure.

FIG. 20 is a photo micrograph of a conductive feature formed accordingto a conventional process.

FIG. 21 is a photo micrograph of a conductive feature formed accordingto an exemplary embodiment of the present disclosure.

For simplicity and clarity of illustration, elements shown in thefigures have not necessarily been drawn to scale. For example, thedimensions of some of the elements may be exaggerated relative to otherelements for clarity. Further, where considered appropriate, referencenumerals may be repeated among the figures to indicate corresponding oranalogous elements.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the disclosure.However, it will be understood by those skilled in the art that thepresent disclosure may be practiced without these specific details. Inother instances, well-known methods, procedures, and components have notbeen described in detail so as not to obscure the present disclosure.

Microchips, printed circuit boards, solar cells, electronic displays(such as, but not limited to, for example, liquid crystal displays,organic light emitting diode displays, and quantum dotelectro-luminescent displays), and a variety of other electrical oroptical devices and components, may be comprised of multiple overlappinglayers, including patterned layers, of different materials supported bya substrate. Various exemplary embodiments of the disclosure contemplatemethods and devices for forming a patterned layer on a substrate forapplication in the fabrication of electrical and/or optical devicesand/or components. Herein a “device layer” shall refer to a layer of amaterial that, in its final form, which in some instances may bepatterened, comprises a layer in a finished optical and/or electronicdevice and/or component, wherein further, a “patterned device layer”shall refer to such a layer after it has been patterned, and an“unpatterned device layer” shall refer to such a layer before it hasbeen patterned. For example, various exemplary embodiments contemplate apatterned device layer of a conductive material that comprises a set ofconductive lines, for example, as may be fabricated on a substrate aspart of manufacturing a printed circuit board (PCB) or other electroniccomponent. According to embodiments of the disclosure, an unpatterneddevice layer on a substrate, for example without limitation, aconductive layer of copper or other conductive material that overlies anelectrically insulating surface of substrate, may be coated with a“primer” layer comprising an “undercut-reducing” material which has theeffect of reducing undercutting during a wet etching process used toremove the device layer material exposed through an etch mask. Forexample, the undercut-reducing material may be an anti-corrosivematerial, which may comprise materials that exhibit anti-corrosiveproperties with respect to the material of the device layer. Suchanti-corrosive materials may comprise polymers, organic materials,inorganic materials, Schiff bases, or other materials, such as thosedisclosed in International Patent Application Publication Nos.WO2016/193978 A2 and WO2016/025949 A1, the entire contents of each ofwhich are incorporated by reference herein. The anti-corrosive materialmay be blanket-formed or -deposited, or pattern-formed or -depositedover the unpatterned device layer. In various exemplary embodiments, theterms anti-corrosive material and undercut-reducing material may be usedinterchangeably.

Various exemplary embodiments of the present disclosure contemplateforming a primer layer comprising an undercut-reducing material over anunpatterned device layer on a substrate and then forming on thesubstrate an etch mask by forming a patterned layer of an etch-resistmaterial over the primer layer. Other exemplary embodiments of thepresent disclosure contemplate forming an etch mask over an unpatterneddevice layer on a substrate by forming on the substrate a patternedlayer of a mixture of an undercut-reducing material and an etch-resistmaterial over an unpatterned device layer without the need for forming aseparate layer, for example a primer layer, comprising anundercut-reducing material. In exemplary embodiments, a primer layercontaining an undercut-reducing material is formed over an unpatterneddevice layer on a substrate and then an etch mask is formed over theprimer layer by applying to or depositing onto the primer layer a liquidetch-resist ink in a pattern and then converting the liquid ink into theetch mask via subsequent processing, for example, by drying or bakingthe ink to form a solid patterned layer of the etch-resist material,wherein such liquid etch-resist ink may comprise a material thatinteracts with the primer layer. For example, the liquid etch-resist inkmay, upon contact with the primer layer, undergo a chemical reactionthat constrains the translation or spread of the ink on the primersurface, e.g. via chemical reaction. In a further example, the liquidetch-resist ink may be applied to the surface in the form of dropletsdelivered by an inkjet nozzle, and upon contact with the primer surface,such droplets may be soon after effectively immobilized or “frozen” inplace such that further translation or spreading of the ink droplet onthe primer surface is greatly reduced or stopped entirely, as describedin International Publication Nos. WO2016/193978 A2 and WO2016/025949 A1,the entire contents of each of which are incorporated by referenceherein. In exemplary embodiments, constraining the spread of theetch-resist ink on the primer surface, for example via a chemicalreaction resulting from the interaction between the etch-resist ink andthe primer layer, may contribute to accurate deposition of mask patternsover the layer to be patterned.

In exemplary embodiments, a primer layer is formed over an unpatterneddevice layer on a substrate, and an etch mask is formed over the primerlayer by delivering a liquid etch-resist ink onto the primer layer in apattern and then converting the liquid ink into the etch mask viasubsequent processing, for example, by drying or baking the ink to forma solid patterned layer resistant to subsequent etching. In exemplaryembodiments, the primer layer comprises a first reactive component, theliquid etch-resist ink comprises a second reactive component, and whenthe etch-resist ink makes contact with the primer layer, the first andsecond reactive components react to effectively immobilize or “freeze”in place the ink so that further translation or spreading of the ink onthe primer surface is greatly reduced or stopped entirely. In exemplaryembodiments, the primer layer comprises a third reactive component, theliquid etch-resist ink comprises a fourth reactive component, and thereaction of the third and fourth reactive components produces an etchmask material that is relatively insoluble in the etch-resist ink andrelatively insoluble in the etch solution used to subsequently etch theunpatterned device layer (wherein relatively insoluble is here definedwith respect to the fourth reactive component). The etch mask materialso formed is referred to herein as a bi-component material or abi-component reaction product. In various embodiments, the reactivecomponent that provides the majority of the mass to form bi-componentmaterial that makes up the etch mask is referred to as the etch-resistcomponent, or equivalently, the etching-resisting component, while theother reactive component is referred to as the fixating component, orequivalently, the fixating reactive component or fixating composition.In exemplary embodiments, the etch-resist component comprises multiplematerials. In exemplary embodiments, the fixating component comprisesmultiple materials. In exemplary embodiments, the etch-resist ink is anaqueous ink, and the bi-component material is relatively insoluble inwater. In exemplary embodiments, the etch solution is an acidic etchsolution, for example without limitation, a mixture of copper chlorideand hydrogen peroxide. In exemplary embodiments, one or more of thefirst, second, third, or fourth components comprise multiple materials.In exemplary embodiments, the first and third components are the same.In exemplary embodiments, the second and fourth components are the same.In exemplary embodiments, the reaction that produces the bi-componentmaterial is the same as the reaction that immobilizes the droplets ofthe etch-resist ink on the primer layer. In exemplary embodiments, theprimer layer comprises an undercut-preventing material. In exemplaryembodiments, a reactive component of the primer (e.g. the first or thirdreactive component described above) comprises an undercut-preventingmaterial. In exemplary embodiments, a reactive component of theetch-resist ink (e.g. the second or fourth reactive component describedabove) comprises an undercut-preventing material. In exemplaryembodiments, the etch-resist ink comprises an undercut-preventingmaterial.

In exemplary embodiments, at least one of the primer or the etch-resistink may comprise multivalent and/or poly-cationic groups and/ormultivalent inorganic cations. In exemplary embodiments, at least one ofthe primer or the etch-resist ink may comprise poly-anionic groups. Inexemplary embodiments, at least one of the primer or the etch-resist inkmay comprise reactive anionic components and be water soluble. Inexemplary embodiments, such reactive anionic components may include atleast one anionic polymer (in a base form) at pH higher than 7.0. Inexemplary embodiments, such anionic polymer may be selected from acrylicresins and styrene-acrylic resins in their dissolved salt forms (forexample without limitation, sodium salt form), sulphonic resins in theirdissolved salt forms (for example without limitation, sodium salt form).In exemplary embodiments, such anionic polymer may be in an ammoniumform or an amine neutralized form. In exemplary embodiments, suchanionic polymer may be in the form of a polymer emulsion or dispersion.In various embodiments, the reaction that produces the bi-componentmaterial causes a large increase in the viscosity of the etch-resist inkon the primer layer, and the immobilization phenomenon resultssubstantially from this increase in viscosity. In various embodiments,the etch-resist ink provides a majority of the material mass that formsthe bi-component material. In various embodiments, the primer provides amajority of the material mass that forms the bi-component material, andin such cases, the primer layer may contain the etch resist componentwhile the etch resist ink may contain the fixating component. In variousembodiments, the primer layer is formed by providing a coating of aliquid primer ink over the unpatterned device layer and thensubsequently processing the layer to form the primer layer, e.g. bydrying or baking the layer. In various embodiments, such primer ink isaqueous. In various embodiments, the primer layer has good adhesion tothe unpatterned device layer. In various embodiments, the primer layeris applied over the unpatterned device layer by inkjet printing, spraycoating, metered rod coating, roll coating, dip coating, or any othersuitable printing or coating method. In various embodiments, the primerlayer may be a uniform (e.g. blanket) coating or may be a patternedcoating.

In exemplary embodiments, the primer layer is formed at least in part byapplying a surface activating solution over the unpatterned devicelayer. In exemplary embodiments, the surface activating solutioncomprises one or more of copper salts, ferric salts, chromic-sulfuricacids, persulfate salts, sodium chlorite, and hydrogen peroxide. Inexemplary embodiments, the unpatterned device layer is a metal layer andthe surface activating solution is applied onto the surface of the metallayer. In exemplary embodiments, the surface activating solution may beapplied for a predetermined time and then washed off, for examplewithout limitation, for 10 seconds, 20 seconds, 30 seconds, 60 seconds,or longer times. In exemplary embodiments, the surface activatingsolution may be applied by immersing the surface into a bath containingthe surface activating solution. In exemplary embodiments, the surfaceactivating solution may be applied by spraying the surface with thesurface activating solution, or any other suitable method. In exemplaryembodiments, the surface activating solution is washed off the surfaceusing a washing fluid, for example without limitation, an alcoholsolution, ethanol, propyl alcohol, iso-propyl alcohol, and acetone. Inexemplary embodiments, wherein the surface is the surface of a copperlayer, for example of a PCB, a surface activating aqueous solution ofCuCl₂ (or any divalent copper salt) at a weight percent concentration of0.5 to 1.0 is utilized, and the primer layer is formed at least in partby immersing the copper surface in a bath containing the surfaceactivating solution for 30 seconds. In exemplary embodiments, whereinthe surface is the surface of a copper layer, for example of a PCB, asurface activating aqueous solution of Na₂S₂O₈ (or any persulfate salt)at a weight percent concentration of 0.5 to 1.0 is utilized, and theprimer layer is formed at least in part by immersing the copper surfacein a bath containing the surface activating solution for 30 seconds. Inexemplary embodiments, wherein the surface is the surface of a copperlayer, for example of a PCB, a surface activating aqueous solution ofH₂O₂ at a weight percent concentration of 10 is utilized, and the primerlayer is formed at least in part by immersing the copper surface in abath containing the surface activating solution for 30 seconds. Inexemplary embodiments, wherein the surface is the surface of a copperlayer, for example of a PCB, a surface activating aqueous solution ofFeCl₃ at a weight percent concentration of 20 is utilized, and theprimer layer is formed at least in part by immersing the copper surfacein a bath containing the surface activating solution for 10 seconds. Inexemplary embodiments, wherein the surface is the surface of a copperlayer, for example of a PCB, a surface activating aqueous solution ofHCrO₄/H₂SO₄ at a weight percent concentration of 5 is utilized, and theprimer layer is formed at least in part by immersing the copper surfacein a bath containing the surface activating solution for 30 seconds. Inexemplary embodiments, wherein the surface is the surface of a copperlayer, for example of a PCB, a surface activating aqueous solution ofNaClO₂ at a weight percent concentration of 5 is utilized, and theprimer layer is formed at least in part by immersing the copper surfacein a bath containing the surface activating solution for 60 seconds.

In exemplary embodiments of printing an etch-resist ink onto a primerlayer using an inkjet printer, the substrate may be at approximately“room” temperature, e.g. in the range of 20° C. to 30° C., or may be atelevated temperature, e.g. as high as 100° C. In exemplary embodiments,a bi-component etch mask may have a thickness of at least 0.01 um. Inexemplary embodiments, a bi-component etch mask may have a thicknessless than 12 um.

In exemplary embodiments of the disclosure, a primer layer is depositedonto a substrate and an etch mask ink is subsequently deposited onto theprimer layer using inkjet printing and then baked to form an etch masklayer. Soon after contacting the primer layer, droplets of the etch maskink interact with the primer layer so as to effectively immobilize or“freeze” the droplets of ink such that further spreading and/ortranslation is greatly reduced or eliminated, as a result of a chemicalreaction between a first reactive component in the primer layer and asecond reactive component in the etch mask ink. Furthermore, one or morecomponents of the etch mask ink undergoes a reaction with one or morecomponents of the primer layer to form a bi-component etch mask materialthat is relatively insoluble in the etch mask ink and relativelyinsoluble in the etch solution with which the etch mask will be used(wherein relatively insoluble is here defined with respect to the etchmask ink components that react to form the bi-component etch maskmaterial.) For example, the etch mask ink may be aqueous and the etchmask material resulting from such reaction is insoluble in water, and,the etch solution may be an acidic etch solution and the etch maskmaterial resulting from such reaction is insoluble in the acidic etchsolution.

In exemplary embodiments, coating an unpatterned device layer, such as acopper layer, with an undercut-preventing material, such as ananti-corrosive material, may be applicable to any process that uses anetch mask to protect the device layer material from being wet-etched.Other metal layers instead of copper may be used in exemplaryembodiments, including but not limited to, for example, aluminum,stainless steel, gold, and metallic alloys. Exemplary embodiments of thedisclosure include introducing the undercut-reducing material in theform of a primer layer prior to applying a photo-resist layer to anunpatterned device layer, for example, via lamination, slot die coating,or spin coating, that is subsequently patterned via exposure to selectedwavelengths of light, for example UV light, through a photomask, or viadirect laser imaging.

Action of the undercut-reducing material during a chemical etch processmay mitigate (e.g., reduce, eliminate) the occurrence of undercut of thedevice layer features resulting from the patterning process. Thus, aftera chemical etch process is performed, device layer features withsidewalls that are more vertical and less sloped as compared to a devicelayer formed without an undercut-reducing material may be formed due toreduction or elimination of the undercutting. When applied to apatterned device layer comprising a conductive material having thefunction of carrying electrical current or electrical signals, variousembodiments of the disclosure may enhance the overall performance of theso-formed electrical circuitry, improve the overall conductivity of theindividual conductive features, enhance frequency response, and enablethe manufacturing of a pattern with higher density and both thinnerfeatures and thinner spaces between features. Analogous benefits alsomay be derived in components using patterned device layers ofnon-metallic materials, such as optical or insulating patternedfeatures.

It is believed that during conventional wet-etching processes, as aliquid etchant advances down (e.g., in a direction toward a substrate)through a thickness of a device layer material being etched in thoseareas not covered by an etch mask, the liquid etchant also advanceslaterally into the lateral surface (e.g. side wall) of those portions ofthe device layer material covered by an etch mask. As the etching depthincreases, more of the side wall is exposed to lateral etching, suchthat the portions of the side wall closest to the etch mask are exposedto the liquid etchant for a longer period of time than the portions ofthe side wall closest to the substrate, and accordingly are subject toincreased lateral etching, thus imparting to the sidewalls of theresulting patterned device layer features an undercut shape. In otherwords, the time the etchant reacts with the device layer material toremove the portions of the device layer material increases with thedistance from the substrate. While not wishing to be bound by anyparticular theory, it is believed that in conventional wet-etchingprocesses, whether carried out by immersion or by jetting or sprayingthe etchant, the additional reaction time between the etchant andportions of the device layer material further from the substrate resultsin an erosion (removal) of the device layer material laterally inward inregions of the device layer material directly under and proximate theetch mask features, despite that the intent of the etch mask is toprevent the removal of the device layer material in those areas. Furtherexplanation and depictions of this phenomenon are provided below inconnection with FIGS. 4B-5C.

As discussed in various exemplary embodiments in accordance with thepresent disclosure, reaction between the etchant and portions of thedevice layer material corresponding to lateral surfaces, orequivalently, side walls, of a patterned device layer feature ismitigated (e.g., reduced, prevented, inhibited) during a wet etchprocess, thereby mitigating the formation of an undercut shape on thelateral surfaces.

FIGS. 1A-5C all illustrate various stages of processing a device to forma patterned device layer on a substrate, or equivalently, patterneddevice layer features on a substrate, according to various conventionalprocesses. In an exemplary embodiment, the device is a PCB in theprocess of being manufactured and the device layer material is anelectrically conductive material. However, those having ordinary skillin the art will appreciate reference to a PCB is non-limiting andexemplary only and that a variety of applications are encompassed withinthe scope of the present disclosure, such as various electronic andoptical components referenced above. Referring now to FIGS. 1A-1D,various views of a device 100 undergoing processing to form patterneddevice layer features according to one conventional process is shown.FIG. 1A is a plan view and side view of a device 100 comprising asubstrate 102 with an unpatterned device layer 104 disposed on thesubstrate 102.

Substrate 102 may itself comprise multiple layers, for example withoutlimitation, one or more unpatterned or patterned device layers. Forexample, while the unpatterned device layer 104 is shown on one side(e.g. the “top” in the orientation of the figures) of the substrate 102,this disclosure also contemplates “double-sided” processing of device100, for example, wherein substrate 102 comprises a second unpatterneddevice layer situated so as to comprise the opposing side (e.g. the“bottom”) of the substrate 102. In exemplary embodiments, such “bottom”side unpatterned device layer is subject to a similar patterning processas the “top” side unpatterned device layer 104, and such “bottom” sidepatterning occurs in whole or in part before, after, or during the “top”side patterning of unpatterned device layer 104. In exemplaryembodiments, substrate 102 may comprise one or more patterned devicelayers processed according to one or more exemplary embodiments, forexample without limitation, in a manner similar to the manner used toprocess unpatterned device layer 104.

In one exemplary embodiment, device 100 is a PCB in the process ofmanufacturing, unpatterned device layer 104 comprises an electricallyconductive material, thereby making it an unpatterned electricallyconductive device layer, substrate 102 comprises one or more layers ofelectrically insulating material configured to provide a “top”electrically insulating surface and a “bottom” electrically insulatingsurface, and the unpatterned electrically conductive device layer 104 issituated to be adjacent to the “top” electrically insulating surface. Asecond unpatterned electrically conductive device layer is incorporatedinto substrate 102 and situated to be adjacent to the “bottom”electrically insulating surface (wherein such “bottom” electricallyinsulating surface is within substrate 102 and not shown in FIG. 1), andthe “bottom” surface of substrate 102, namely the surface on theopposite side of substrate 102 relative to the surface adjacent tounpatterned device layer 104, is a surface of the second unpatternedelectrically conductive device layer.

In one exemplary embodiment, device 100 is a PCB in the process of beingmanufactured, and substrate 102 has an electrically insulating surfaceover a region comprising at least a portion of the interface betweensubstrate 102 and unpatterned device layer 104. In one exemplaryembodiment, substrate 102 may comprise a layer of an electricallyinsulating material such as, for example and without limitation,composite materials including woven glass bonded by epoxy resins orother materials. Such electrically insulating material may have, forexample, a thickness in a range from about 0.001 inches to about 0.05inches. In one exemplary embodiment, substrate 102 may comprise multiplealternating layers of electrically insulating material and electricallyconductive material, further comprising at least two electricallyinsulating layers, each layer comprising woven glass bonded by epoxyresins or other materials and having a thickness between 0.001 inchesand 0.05 inches, for example, one “core” layer and one layer comprisinga pre-impregnated bonding sheet (which may be referred to as a“PrePreg”), and at least one patterned electrically conductive layersituated in between the electrically insulating layers, wherein the“top” surface of substrate 102 interfacing with unpatterned device layer104 is a surface of one of the at least two electrically insulatinglayers. In an exemplary embodiment, a PrePreg comprises an FR4 gradeepoxy laminate sheet. In an exemplary embodiment, a core layer comprisesan FR4 grade epoxy laminate sheet.

The unpatterned device layer 104 may comprise a layer of conductivematerial, such as, for example, a metal or metal alloy including but notlimited to copper, aluminum, silver, gold, or other conductive materialswith which those having ordinary skill in the art are familiar. In anexemplary embodiment, the unpatterned device layer 104 is a copper foillaminated onto substrate 102, wherein the interface surface betweensubstrate 102 and unpatterned device layer 104 is electricallyinsulating; however, other conductive materials are considered withinthe scope of this disclosure.

Referring now to FIG. 1B, in a next stage of processing, an etch mask106 is formed on the exposed surface 110 of the unpatterned device layer104. The etch mask 106 may be formed in a desired pattern 108, such aslines corresponding to where patterned device layer lines are desired onthe device 100 following processing, as shown in FIG. 1B. Stated anotherway, the etch mask 106 may comprise etch-resist material deposited overthe unpatterned device layer 104 in locations corresponding to wherepatterned device layer features are desired in the device 100. The etchmask 106 may comprise a material such as, for example, a polymer, anoxide, a nitride, or other materials. In one exemplary embodiment, theetch mask material is a polymer that is formed using a negative tonephoto-resist material, for example without limitation, one of the SU-8series of photoresists supplied by MicroChem Corp., 200 Flanders Road,Westborough, Mass. 01581 USA. In one exemplary embodiment, the etch maskmaterial is a polymer that is formed using a positive tone photo-resistmaterial, for example without limitation, one of the ma-P 1200 seriesphotoresists supplied by micro resist technology GmbH., Köpenicker Str.325, 12555 Berlin, Del. The etch mask 106 may be patterned over thesurface of the unpatterned device layer 104 by methods such assilkscreen printing, inkjet printing, photolithography, gravureprinting, stamping, photoengraving, or other methods. After the etchmask 106 is applied to the surface 110 of the unpatterned device layer104, the device 100 is exposed to an etchant, such as a chemicaletchant, that removes the material in unpatterned device layer 104 fromthose areas not protected by the etch mask 106, resulting in theformation of patterned device layer 114, as shown in FIG. 1C. Such achemical etchant may comprise chemical compounds that have a corrosiveeffect on the material of the unpatterned device layer 104. In exemplaryembodiments, unpatterned device layer 104 is an electrically conductivelayer and such a chemical etchant may comprise, without limitation,ammonium persulfate, ferric chloride, or other chemical compounds thathave a corrosive effect on the material of the unpatterned device layer104. In one embodiment, the unpatterned electrically conductive devicelayer 104 comprises copper, and the etchant used is copper chloride(CuCl₂). Those having ordinary skill in the art are familiar withvarious chemical etchants suitable for removal of the material of theunpatterned device layer 104.

With continued reference to FIG. 1C, when the unpatterned device layer104 is exposed to the etchant, the etchant dissolves (e.g., corrodes)the material of the unpatterned device layer 104 beginning with theexposed top surface 110. As the material of the unpatterned device layer104 is removed, the etchant may also remove portions of the material ofthe unpatterned device layer 104 underneath the etch mask 106, leavingnon-straight, and non-perpendicular sidewalls 112. For example, as shownin FIG. 1C, in the device 100 produced according to the process shown inFIGS. 1A-1D, the sidewalls 112 of a feature of patterned device layer114 produced according to the pattern 108 of the etch mask 106 mayexhibit a tapered shape, e.g., tapering from a first feature width W1 atan interface between the patterned device layer 114 and the etch mask106, to a second feature width W2 wider than the first feature width W1at an interface between the substrate 102 and the patterned device layer114. FIG. 1D shows the device 100 after the etch mask 106 is removed,exposing the patterned device layer 114. The tapered shape exhibited inFIG. 1D by the sidewalls 112 of the feature of the patterned devicelayer 114 is one illustration of sidewalls that are “undercut,” and willbe discussed in further detail in connection with FIGS. 4A-4C below.Other shapes and arrangements of undercut sidewalls also may occur andinclude sidewalls that are not substantially straight and do not extendsubstantially perpendicular to the surface of the substrate on whichthey are formed.

Referring now to FIGS. 2A-2C, a method of forming an etch mask 206having a pattern 208 of conductive lines is shown. A device 200 having asubstrate 202 and an unpatterned device layer 204 is covered over theentire area (i.e., blanket coated) of the unpatterned device layer 204with unpatterned etch-resist layer 216. The unpatterned etch-resistlayer 216 is then exposed to light (e.g., UV light) in a pattern so thatthe exposed regions are made relatively less susceptible to removal in asubsequent development process (so-called negative-tone processing) orso that the exposed regions are made relatively more susceptible toremoval in a subsequent development process (so-called positive-toneprocessing). Such pattern-wise using light exposure may be accomplished,for example, by shining light through a photo-mask, as in so-calledphotolithographic processing, or by delivering to the etch-resist layer216 a sequence of pulses or scans of a focused light, e.g. in the formof a laser beam, in a pattern as a function of time, so-calleddirect-write processing. The development process removes the material inthe unpatterned etch-resist layer 216 in correspondence with thepattern-wise light exposure resulting in the patterned etch mask 206,having the pattern 208, as shown in FIG. 2C. The development process mayinclude submerging the device 200 in a liquid developer that dissolvesor corrodes the material in the unpatterned etch mask layer 216 where itis relatively more susceptible to removal, for example withoutlimitation, in the case of a negative tone process, the developer liquidmay dissolve the material in the unpatterned etch-resist layer 216 whereit has not been exposed to UV light, whereas in the case of a positivetone process, the developer liquid may dissolve the material in theunpatterned etch-resist layer where it has been exposed to UV light.Removal of portions of the unpatterned device layer 204 not protected bythe etch mask 206 then proceeds as discussed above in connection withFIG. 1D, resulting in the device 200 with a patterned device layerhaving features in the pattern 208 and exhibiting undercutting.

Alternatively, the etch mask may be deposited directly on theunpatterned device layer in the desired pattern, with no intermediatestep of patterning an unpatterned etch-resist layer as in the embodimentof FIGS. 2A-2C. For example, with reference now to FIGS. 3A and 3B, anetch mask 306 may be formed over an unpatterned device layer 304 ofdevice 300 directly in a desired pattern 308 of lines corresponding towhere features of patterned device layer are desired on the resultingdevice. The etch mask 306 may be deposited on the unpatterned devicelayer 304 in the desired pattern 308 by, for example, inkjet printing,laminating, screen printing, gravure printing, stamping, or othermethods. In one exemplary embodiment, etch mask 306 is formed overunpatterned device layer 304 using inkjet printing, wherein an inkjetprinthead having a plurality of nozzles ejects droplets of a liquidetch-resist ink onto the device 300 so as to form a coating of liquidetch resist ink in correspondence with the pattern 308, and such coatingof liquid etch resist ink is subsequently processed so as to convert theliquid coating into the etch mask 306. In one exemplary furtherembodiment, the processing of the liquid etch resist ink comprisesdrying and/or baking the device so as to form a solid etch mask 306 fromthe liquid coating. In one exemplary embodiment, etch mask 306 is formedover unpatterned device layer 304 using an inkjet printer comprising oneor more printheads comprising a plurality of nozzles, a substratesupport that holds the substrate, a stage for relatively moving theplurality of nozzles and the substrate, a motion control system forcontrolling the relative position of the substrate and the nozzles, anda nozzle control system for controlling the firing of the nozzles so asto deliver droplets onto the substrate in the desired pattern. It iscontemplated in this disclosure that in any embodiment wherein inkjetprinting is utilized to deposit a liquid coating, an inkjet printingsystem such as described here may be used.

FIGS. 4A-4C illustrate a conventional process for removing material froman unpatterned device layer 404 from a device 400 and depicts what isbelieved to occur during a wet-etching process that causes undercutting.In FIG. 4A, the unpatterned device layer 404 is covered by etch mask 406in correspondence with pattern 408. The device 400 is then exposed to achemical etchant 418. In the exemplary embodiment of FIG. 4B, theexposure occurs by immersion in the etchant 418. The etchant 418 removesmaterial from the unpatterned device layer 404 (from FIG. 4A) to createpartially patterned device layer 405. For example, in the embodiment ofFIG. 4B, the etchant 418 comprises a liquid, for example withlimitation, a solution, contained within a vessel 420, and the device400 with the etch mask 406 (FIG. 4B) is immersed in the etchant 418, asshown in FIG. 4B. Once the exposed portion of top surface 410 (FIG. 4A)of the unpatterned conductive layer 404 is etched away and a sidewall412 begins to form, the sidewall 412 is exposed to the etchant 418 andthe etchant 418 removes material from the sidewall 412, leading to thetapered, undercut shape of the feature of the patterned device layer 414shown in FIG. 4C. Stated another way, the etchant 418, which may actuniversally in all directions, attacks the material comprising thedevice layer (whether the device layer is in its unpatterned, i.e. 404,partially patterned, i.e. 405, or patterned, i.e. 414, state) laterallyunderneath the etch mask 406 as soon as the top surface 410 ofunpatterned device layer 404 is etched away. The amount of the materialof the device layer removed by the etchant 418 may be dependent upon theamount of time to which the material of the device layer is exposed tothe etchant 418. Thus, as the etchant 418 advances through a thicknessof the partially patterned device layer 405 (i.e., in the directionnormal to the plane of substrate 402), the portions of the sidewalls 412closer to the etch mask 406 are exposed to the etchant 418 for a longertime period than the portions of the sidewalls 412 closer to substrate402, and the etching process thereby imparts to the sidewalls 412 thetapered (i.e., undercut) shape shown in FIG. 4C. In other words, thetime the etchant reacts with the material in the device layer to removesuch material from the device layer increases with the distance from thesubstrate. While not wishing to be bound by any particular theory, it isbelieved therefore that the additional reaction time between the etchantand material in those portions of the device layer further from thesubstrate results in an erosion (removal) of the material from thedevice layer laterally inward in regions of the device layer directlyunder and proximate the etch mask, despite that the intent of the etchmask is to prevent the removal of the material of the device layer inthose areas.

Referring now to FIG. 5A-5C, an embodiment of another conventionalprocess is shown. The process of FIGS. 5A-5C is similar to thatdescribed in connection with FIGS. 4A-4C, and includes forming an etchmask 506 over an unpatterned device layer 504 of a device 500, as shownin FIG. 5A. Rather than immerse the device 500 within the etchant 518,as described above in connection with FIG. 4B, the etchant 518 isintroduced in jets 522 that impinge the device 500, which may be in avessel 520, as shown in FIG. 5B. Excess etchant 518 can flow into adrain 524 of the vessel 520 or otherwise be collected, e.g., forrecirculation or other processing. Because the etchant 518 actsomnidirectionally, a taper or undercut forms on the resulting sidewall512 of the feature of patterned device layer 514, as shown in FIG. 5C.

As discussed above, having the undercut sidewalls of the features of thepatterned device layer formed on a device introduce various limitationson the size and shape of features that may be formed. For example, asdiscussed above, the tendency for undercuts to form may impose limits onthe minimum feature width or minimum feature-to-feature spacing capableof being produced, thereby limiting feature density on the device. Invarious applications, maximizing feature density on the device improvesperformance. In various embodiments, the device layer comprises anelectrically conductive material, the device is a PCB, and the tendencyfor undercuts may limit the minimum feature width, the minimumfeature-to-feature spacing, and the maximum feature density.

FIGS. 6A-17 show various embodiments of processes for mitigating (e.g.,reducing or eliminating) the undercut that occurs during conventionalprocessing. For example, with reference now to FIG. 6A, a device 600 hasan unpatterned device layer 604 over substrate 602. The unpatterneddevice layer 604 may be applied to the substrate by chemical vapordeposition, physical vapor deposition, laminating, slot die coating,spin coating, inkjet printing, screen printing, nozzle printing, gravureprinting, rod coating, or any other suitable method, as those havingordinary skill in the art are familiar. The unpatterned device layer 604is coated with an anti-corrosive layer 629 prior to forming the etchmask 628 above the anti-corrosive layer 629. The anti-corrosive layer629 may be applied to the substrate by chemical vapor deposition,physical vapor deposition, laminating, slot die coating, spin coating,inkjet printing, screen printing, nozzle printing, gravure printing, rodcoating, or any other suitable method, as those having ordinary skill inthe art are familiar. In some embodiments, the anti-corrosive layer 629comprises a “primer” layer, and the etch mask 628 is formed bydepositing onto the primer layer a liquid etch-resist ink which isconverted into the etch mask 628 via subsequent processing, for examplewithout limitation, drying or baking. In various embodiments, asdescribed previously, such liquid etch-resist ink may be delivered tothe device 600 in the form of droplets via inkjet printing and mayinteract with the anti-corrosive layer 629 (which in such case isfunctioning as a primer layer) in a manner that such droplets, uponcontact with the primer surface are rapidly (e.g., on the order ofmicro-seconds) effectively immobilized or “frozen” in place such thatfurther translation or spreading of the ink droplet on the primersurface is greatly reduced or stopped entirely, as discussed further inInt'l Pub. Nos. WO2016/193978 A2 and WO2016/025949 A1, incorporated byreference above. Such a liquid etch-resist ink may further produce viainteraction with such a primer layer a bi-component material that atleast in part forms the etch resist mask

In various embodiments, with reference to FIG. 6A, a device 600 is aPCB, unpatterned device layer 604 comprises an electrically conductivematerial such as copper, aluminum, gold, and/or other metals, and thesurface of substrate 602 adjacent to unpatterned electrically conductivedevice layer 604 is electrically insulating.

In exemplary embodiments, the anti-corrosive layer 629 may comprisematerials chosen based on their ability to impede the corrosive effectsof a chemical etchant used to remove the material of the unpatterneddevice layer 604 of the device 600. As non-limiting examples, theanti-corrosive layer 629 may comprise, without limitation, a polymer, anorganic compound such as an organic compound comprising one or more-imine groups, one or more -amine groups, one or more -azole groups, oneor more -hydrazine groups, one or more amino acids, a Schiff base, orother materials. In other exemplary embodiments, the anti-corrosivelayer 629 may comprise inorganic materials such as a chromate, amolybdate, a tetraborate, or another inorganic compound. In someexemplary embodiments, the anti-corrosive layer 629 may comprise areactive component, such as one or more reactive cationic groupscomprising polycations and/or multivalent cations. The cationic reactivecomponent may be capable of adhering to metallic surfaces, such ascopper surfaces.

In some embodiments, the anti-corrosive layer 629 may be formed byapplying a liquid anti-corrosive ink over the unpatterned device layerusing any known application method, for example without limitation,spraying, spin coating, nozzle printing, rod coating, screen printing,smearing, ink-jet printing or the like, and then processing the device600 so as to convert the liquid coating into the anti-corrosive layer629. In some embodiments, anti-corrosive layer 629 may be referred to asa primer layer, and the liquid anti-corrosive ink may be referred to asa primer ink. The liquid anti-corrosive ink may comprise a solution thatmay include poly-imines such as, for example, polyethyleneimines, suchas linear polyethyleneimines or branched polyethyleneimines, having lowor high molecular weights. As a non-limiting example, the molecularweights may range from about 800 to about 2,000,000.

In some embodiments, to make the liquid anti-corrosive ink jettable viaink-jet printheads, the liquid ink may be an aqueous solution that mayinclude additional agents such as Propylene glycol, n-Propanol and awetting additive (such as TEGO 500 supplied by Evonik Industries).

In some embodiments, the thickness of the anti-corrosive material layer629 may be in a range of from about 0.03 μm to about 1.1 μm. In someembodiments, the method may include drying the applied ink using anydrying method to form a solid coating. In some embodiments, the methodmay include baking the applied ink using any drying method to form asolid coating.

As further non-limiting examples, if present, the cationic reactivecomponent of anti-corrosive material layer 629 may comprise polyamides,such as polyethyleneimine, poly-quaternary amines, long-chain quaternaryamines, poly-tertiary amines at various pH levels and multi-valentinorganic cations such as magnesium cation, zinc cation, calcium cation,copper cation, ferric cation, and ferrous cation. The polymericcomponents may be introduced to the formulation either as solublecomponents or in emulsion form.

The anti-corrosive material layer 629 may be applied to the unpatterneddevice layer 604 using any suitable printing or coating method includingbut not limited to, inkjet printing, spraying, metering rod coating,roll coating, dip coating, spin coating, screen printing, laminating,stamping and others. The anti-corrosive layer 629 may be applieduniformly over the unpatterned device layer 604, or applied in a desiredpattern, such as in the pattern 608 defining the desired pattern of thepatterned device layer 630 (in accordance with FIG. 6.)

In the exemplary embodiment of FIGS. 6A-6D, the anti-corrosive layer 629may comprise a “primer” layer, and the etch mask 628 may be formed bydepositing onto the primer layer a liquid etch-resist ink which isconverted into the etch mask 628 via subsequent processing, for examplewithout limitation, drying or baking. In various embodiments, suchdrying may comprise baking, for example without limitation at 70° C. orhigher. In various embodiments, as described previously, such liquidetch-resist ink may be delivered to the device 600 in the form ofdroplets via inkjet printing and may interact with the primer layer inmanner that such droplets, upon contact with the primer surface arerapidly (e.g., on the order of micro-seconds) immobilized or “frozen” inplace such that further translation or spreading of the ink droplet onthe primer surface is greatly reduced or stopped entirely, as discussedfurther in Int'l Pub. Nos. WO2016/193978 A2 and WO2016/025949 A1,incorporated by reference above. Such a liquid etch resist ink mayfurther produce via interaction with such a primer layer andbi-component material that at least in part forms the etch mask

The etch mask 628, or, a liquid etch-resist ink used to make such etchmask 628 (according to various embodiments as described above) maycomprise polymeric components that are water-soluble and may includeanionic groups. The anionic polymer may be selected from acrylic resinsand styrene-acrylic resins in their dissolved salt forms. The anionicpolymer may be selected from sulphonic resins in their dissolved saltform, such as sodium, ammonium- or amine-neutralized form. Inembodiments utilizing a liquid etch resist ink, the liquid ink mayinclude additional agents for improving the printing or other depositionquality of the material.

The etch mask 628, or, a liquid etch-resist ink used to make such etchmask 628 (according to certain embodiments as described above) maycomprise a reactive component that may be water-soluble and may includereactive anionic groups. Non-limiting examples of anionic reactivecomponents may include at least one anionic polymer (in a base form) atpH higher than 7.0. The anionic polymer may be selected from acrylicresins and styrene-acrylic resins in their dissolved salt forms. Theanionic polymer may be selected from sulphonic resins in their dissolvedsalt form, for example without limitation, sodium salt form, ammonium oramine neutralized form, as well as in the form of a polymer emulsion ordispersion. Polymeric components may be introduced to the formulationeither as soluble components or in emulsion form.

Referring to FIG. 6B, the anti-corrosive layer 629 and the etch mask 628may be directly printed on the device 600. In one exemplary embodiment,the anti-corrosive layer 629 may be formed via printing over theunpatterned device layer 604 in a desired pattern, such as pattern 608,so as to facilitate the fabrication of a correspondingly patterneddevice layer 630 (as in FIG. 6.) The anti-corrosive layer 629 may bedeposited with a thickness ranging from about 5 nm to about 100 nm, ofabout 100 nm or less, or of about 1 μm or less. Other thicknesses of theanti-corrosive material layer 629 are considered within the scope of thedisclosure and may depend on the particular application. The etch mask628 is then formed via printing over the anti-corrosive material layer629 in a desired patterned, such as pattern 608, so as to facilitate thefabrication of a correspondingly patterned device layer 630 (as in FIG.6.). The etch mask 628 may be deposited, for example, so as to have athickness ranging from about 1 μm to about 5 μm, or of about 5 μm orless, or of about 15 μm or less.

The device 600 is then introduced to an etchant, such as a liquidchemical etchant 418 or 518 as discussed in connection with FIGS. 4B and5B. Presence of the anti-corrosive material layer 629 may contribute toa decreased amount of undercutting of a feature of a patterned devicelayer 630, as shown in FIGS. 6C and 6D. For example, the feature ofpatterned device layer 630 may exhibit a first width W1 proximate theanti-corrosive layer 629, and a second width W2 proximate the substrate602. In some exemplary embodiments, a difference between the width W1and W2 results in the feature of patterned device layer 630 exhibitingtapered sidewalls 632 (i.e., the feature of patterned device layer 630may exhibit some degree of undercut). The undercut exhibited by thefeature of patterned device layer 630 may be less than the undercutexhibited by the features of patterned device layers 114, 414 (FIGS. 1Dand 4D) discussed above. Various measurements may be used to quantifythe degree of undercut, as discussed in greater detail below inconnection with FIGS. 10 and 11.

In the exemplary embodiment of FIGS. 7A-7C, an anti-corrosive layer 729is blanket deposited over the surface of an unpatterned device layer 704disposed on a substrate 702. Such blanket coating may be done by methodssuch as, without limitation, chemical vapor deposition, physical vapordeposition, laminating, inkjet printing, spraying, metering rod coating,roll coating, dip coating, spin coating, screen printing, nozzleprinting, or other methods. An etch mask 728 may be formed over theanti-corrosive layer 729 in a desired pattern, such as the pattern 708as discussed with respect to various embodiments above. The methodproceeds similarly to the embodiment of FIGS. 6A-6C described above. Forexample, the device 700 with the anti-corrosive layer 729 and etch mask728 is exposed to an etchant, such as etchant 418 or 518 discussed inconnection with FIGS. 4B and 5B. As shown in FIG. 7B, the device 700 isplaced in a vessel 720, and an etchant 718 is jetted over the surface ofthe device 700 on which the etch mask 728 is disposed. The etchant 718may remove the anti-corrosive layer 729 from the surface of theunpatterned device layer 704 and expose the material of unpatterneddevice layer 704, which is removed by the etchant 718 as shown in FIG.7B, to form patterned device layer 730 having sidewalls 732 exhibiting areduced degree of undercut as compared to sidewalls 112 associated withpatterned device layer 114, 414 produced according to conventionalprocesses. Partially patterned device layer 705 reflects theintermediate state of the device layer after anti-corrosive layer 729has been removed from those regions exposed through the etch mask andsome of the material of the device layer itself has been etched away,and before the etching has progressed sufficiently to form the patterneddevice layer 730.

Referring now to FIGS. 8A-8D, a more detailed illustration of a portionof the process of the embodiment of FIGS. 7A-7C is shown. In FIG. 8A,jets 822 of an etchant (such as etchant 718 in FIG. 7B) impinge thesurface of an anti-corrosive layer 829 and an etch mask 828 that aredeposited on an unpatterned device layer 804 on substrate 802. Theanti-corrosive layer 829 may preferentially adhere to the surface of thematerial of the device layer and may also be at least partially solublein the etchant 718, while the etch-resist material 828 may besubstantially insoluble in the etchant 718. The jets 822 of etchant 718may contain sufficient kinetic energy to remove the anti-corrosive layer829 from the unpatterned device layer 804 in those regions exposedthrough the etch mask, as shown in FIG. 8B, and thereafter the etchant718 may start removing the material of the unpatterned device layer 804not covered by the etch-resist material 828 and form partially patterneddevice layer 805 as shown in FIG. 8C. FIG. 8D shows the device 800 afterthe partially patterned device layer 805 has been sufficiently etched toform patterned device layer 830. As shown in FIG. 8D, patterned devicelayer 830 has sidewalls 832 that exhibit less undercut than thesidewalls produced according to the conventional process described inconnection with FIGS. 1A-5C. While the patterned device layer 830 isshown with a slight undercut in FIG. 8D, the present disclosurecontemplates patterned device layer (e.g., conductive) features withsubstantially no undercut (i.e., substantially straight and extendingperpendicular to the surface of substrate 802).

Referring now to FIGS. 9A-9C, another embodiment of a process forforming a patterned device layer 930 on a device 900 is shown. Anunpatterned device layer 904 disposed over a substrate 902 is maskedwith an anti-corrosive layer 929 and an etch mask 928. The device 900 isintroduced into a vessel 920 with an etchant 918 such that the device isimmersed within the etchant 918 in FIG. 9B. As shown in FIG. 9C, aresulting patterned device layer 930 of the device 900 has sidewalls 932exhibiting a degree of undercut less than an undercut exhibited by theconductive feature 114 (FIG. 1D) associated with a conventional process.

Referring now to FIG. 10, an enlarged view of the device 100 discussedin connection with the conventional methods of FIGS. 1A-5C is shown. InFIG. 10, the feature of the patterned device layer 114 exhibits atapered sidewall extending between an interface of the etch mask 106 andthe patterned device layer 114 and an interface between the patterneddevice layer 114 and the substrate 102. The patterned device layerfeature 114 exhibits a first width W1 at the interface of the patterneddevice layer 114 and the etch mask 106 and a second width W2 at theinterface of the patterned device layer 114 and the electricallyinsulating substrate 102. FIG. 10 is drawn for illustrative purposes andvariations of the profile can occur, but generally the patterned devicelayer 114 has a wider width at the interface with the substrate than theinterface with the etch-resist material. It is noted that etch mask 106has a width W3 which this disclosure contemplates being greater than,less than, or the same as width W2.

Referring now to FIG. 11, an enlarged view of a device 1100 similar tothe device 600, 700, 800, or 900 shown in FIGS. 6A-9C is shown. In thisexemplary embodiment, the feature of the patterned device layer 1130exhibits a first width W1 at the interface between the patterned devicelayer 1130 and an anti-corrosive layer 1129, and a second width W2 atthe interface between the patterned device layer 1130 and the substrate1102. It is noted that etch mask 1128 has a width W3 which thisdisclosure contemplates being greater than, less than, or the same aswidth W2.

An exemplary measure for the degree of undercut is the etch factor F,which is a ratio of the difference in the widths of the widest andnarrowest parts of the feature of the patterned device layer and theheight of the feature of the patterned device layer. Accordingly, theetch factor F is defined as H/X where H is the height of the line (H)and X equals (W₂−W₁)/2, namely, the difference between of the baseportion width (W2) and the top portion width (W1) divided by two. FIG.11 graphically demonstrates the relations between H and X. Exemplaryvalues of etch factors F for features of patterned device layers of thepresent disclosure are discussed below with Examples 1-3. Asnon-limiting examples, features of device layers associated with devicesmanufactured according to various exemplary embodiments of the presentdisclosure may exhibit etch factors F of greater than 2, greater than 5,greater than 7, or more, such as greater than 10, greater than 20, etc.As a further example, an etch factor F of a conductive feature withsidewalls approaching a vertical line (i.e., exhibiting no undercut)would approach infinity as the value of X approaches zero. Measurementsof H, W1, and W2 may be performed using a variety of microscopytechniques that measure surface profiles, cross sections, and filmthicknesses, for example and without limitation, surface profilometry,scanning electronic microscopy, ellipsometry, and confocal microscopy.

While not wishing to be bound by a particular theory, the inventorsbelieve that portions of the anti-corrosive material layer dissociatefrom the layer and adhere to and/or adsorb onto the side wall of thedevice layer under the etch mask during the etching process so as tomitigate undercutting. FIGS. 12A and 12B depict this phenomenon.

FIG. 12A shows a cross-sectional view of a device 1200 during anintermediate processing step in a patterning process in accordance withvarious exemplary embodiments of the present disclosure. As shown, apartially patterned device layer 1205 on a substrate 1202 is undergoingan etching process. FIG. 12B shows an enlarged view of a portion of FIG.12A at an interface between a sidewall 1232 of a partially patterneddevice layer 1205 and an anti-corrosive layer 1229. As shown in FIG.12B, when the device 1200 is exposed to etchant 1218, a portion 1246 ofthe anti-corrosive material comprising the anti-corrosive layer 1229dissociates from anti-corrosive layer 1229 due to the action of theetchant 1218, for example without limitation, by partially dissolvingthe anti-corrosive layer, and such anti-corrosive material then travelsto and adheres to and/or adsorbs onto the sidewall 1232. Stated anotherway, the presence of the etchant 1218 may facilitate transfer of aportion 1246 of the anti-corrosive material comprising theanti-corrosive layer 1220 from the anti-corrosive material layer 1229 tothe sidewall 1232 of the partially patterned device layer 1230 duringthe etching process. Presence of the anti-corrosive material portion1246 on the sidewall 1232 may then inhibit the corrosive action of theetchant 1218 on the sidewall 1232, thereby decreasing (e.g., reducing oreliminating) the amount of undercut exhibited in the resulting patterneddevice layer 1230. In various exemplary embodiments, it is believed thatat least two processes contribute to these phenomena, wherein in oneprocess the anti-corrosive material is dissolved by the etchant and inanother, simultaneous process, the anti-corrosive material dissolved inthe etchant is adsorbing onto and/or adhering to the sidewall 1232. Invarious exemplary embodiments, the rates of the first and the secondprocesses are such that anti-corrosive material portion 1246 is formedand maintained during the etching process so as to decrease (e.g. reduceor eliminate) the amount of resulting undercut.

As shown in FIG. 12B, it is believed that in some cases the portion ofanti-corrosive material 1246 adsorbed to the sidewall 1232 may exhibit agenerally tapered shape, in which the adhered and/or adsorbed layer 1246of the anti-corrosive material exhibits greater thickness proximate theanti-corrosive material layer 1229 and a reducing thickness along thelayer 1246 in a direction away from the anti-corrosive material layer1229 and toward the substrate.

FIGS. 13A, 13B, and 13C show an additional example of a process in whichit is believed that particles 1348 of an anti-corrosive materialdissociate from anti-corrosive layer 1329 and adhere to and/or adsorbonto a sidewall 1332 of a partially patterned device layer 1305 of adevice 1300. FIGS. 13B and 13C show enlarged views of an interfacebetween an anti-corrosive material layer 1329 and the partiallypatterned device layer sidewall 1332. As shown in FIG. 13B, particles1348 of the anti-corrosive material dissociate from the anti-corrosivematerial layer 1306. In FIG. 13C, the dissociated particles 1348 adhereto and/or adsorb onto the sidewall 1332 of the partially patterneddevice layer 1305. The dissociated particles 1348 may adhere to and/oradsorb onto the sidewall 1332 in a pattern that generally decreases inthickness in a direction away from the anti-corrosive material layer1329. It is believed that in various cases, the dissociated particles1348 may adsorb onto and/or adhere to the sidewall 1332 in asubstantially even pattern, a substantially random pattern, or in someother pattern. The presence of the particles 1348 on the sidewall 1332may inhibit the action of an etchant 1318 and mitigate (e.g., reduce oreliminate) the undercut that occurs on the partially patterned devicelayer 1305 during the etching process. As described above with respectto FIG. 12, in various exemplary embodiments, it is believed that atleast two processes contribute to these phenomena, wherein in oneprocess the anti-corrosive material is dissolved by the etchant and inanother, simultaneous process, the anti-corrosive material dissolved inthe etchant is adsorbing onto and/or adhering to the sidewall 1332, andin various embodiments the rates of the first and the second process aresuch that anti-corrosive material portion 1346 is formed and maintainedduring the etching process so as to decrease (e.g. reduce or eliminate)the amount of undercut observed.

FIG. 14 is a flow chart showing an exemplary embodiment of a work flow1400 for forming a device, for example and without limitation, anelectrical or optical component or device, according to the disclosure.At 1402, an unpatterned device layer is prepared on a substrate. Forexample, an unpatterned device layer, for example a conductive film, islaminated or otherwise deposited onto an electrically insulating surfaceof a substrate. At 1404, an undercut-resistant etch mask is formed, suchas by depositing an anti-corrosive layer on the unpatterned device layerand depositing an etch mask over the anti-corrosive material. Forexample, a liquid primer ink containing an anti-corrosive material isblanket coated onto the substrate and then dried to form ananti-corrosive primer layer, and a liquid etch mask ink is printed ontothe anti-corrosive primer layer and then dried to form an etch mask.Together, the primer layer and the etch mask form the undercut-resistantetch mask. The undercut-resistant etch mask may comprise ananti-corrosive layer as discussed in the exemplary embodiments above(such as, for example, anti-corrosive layers 629, 729, 829, 929, 11291229, or 1329) and an etch mask (such as, for example, etch masks 628,728, 828, or 928). The primer layer and the liquid etch mask ink mayinteract to form a bi-component material, as described above. The primerlayer and the liquid etch mask ink may interact so as to effectivelyimmobilize or freeze the ink on the primer surface, as described above.At 1406, a wet etch is performed to remove areas of the unpatterneddevice layer not covered by the etch mask (i.e., exposed portions of theunpatterned device layer). The wet etch can be performed for a durationsufficient to remove the exposed portions of the unpatterned devicelayer, thereby leaving a patterned device layer corresponding tofeatures covered by the etch mask. At 1408, the etch mask is strippedaway, such as by immersing the device in or spraying the device with astream of stripping fluid that is designed to dissolve and therebyremove the etch mask to expose resulting patterned device layers on thedevice. In various further embodiments, the stripping process alsoremoves the anti-corrosive layer under the etch mask.

FIG. 15 is a flow chart showing in greater detail an exemplaryembodiment of a work flow 1500 for forming an undercut-resistant etchmask, such as that discussed in connection with 1404 above, on asubstrate according to the disclosure. At 1502, an anti-corrosive layer,such as, for example, anti-corrosive layer 629, 729, 829, 929, 11291229, or 1329, is formed on a substrate with an unpatterned devicelayer. In the embodiment of FIG. 15, the anti-corrosive layer is formedas a blanket coating (i.e., an unpatterned layer) over the entiresurface of the unpatterned device layer. At 1504, an etch mask, such asetch mask 628, 728, 828, or 928 is formed over the surface of theanti-corrosive layer in a blanket coating. At 1506, the etch-resistmaterial is direct write exposed or photo-exposed, such as by exposingto a pattern of UV light as generally discussed above in connection withFIGS. 2A-2C. At 1508, the etch-resist material is developed to form thepatterned etch mask, such as, for example, by removing the etch-resistmaterial not exposed to the UV light (in the case of a negative toneprocess) or exposed to the UV light (in the case of a positive toneprocess.)

FIG. 16 is a flow chart showing another exemplary embodiment of a workflow 1600 for forming an undercut resistant etch mask on a substrateaccording to the disclosure. At 1602, an anti-corrosive layer, (such as,for example, anti-corrosive layers 629, 729, 829, 929, 1129 1229, or1329) is formed over a substrate with an unpatterned device layer in ablanket coating over the unpatterned device layer. At 1604, a patternedetch mask (such as, for example, etch masks 628, 728, 828, or 928) isprepared over the un-patterned anti-corrosive coating.

FIG. 17 is a flow chart showing another exemplary embodiment of a workflow 1700 of forming a device according to the disclosure. At 1702, anunpatterned device layer, such as for example but not limited to, acopper film is laminated onto an electrically insulating surface of asubstrate. At 1704, an anti-corrosive layer (such as, for example,anti-corrosive layers 629, 729, 829, 929, 1129, 1229, or 1329) is formedin a blanket coating over the copper film. At 1706, an etch mask (suchas, for example, etch resist mask 628, 728, 828, or 928) is prepared byprinting a liquid etch-resist ink in desired pattern over theblanket-coated anti-corrosive material and then drying the liquid toform the etch mask. At 1708, a spray-type wet etch is performed to etchthe areas of the copper film not covered by the etch mask material. At1710, the etch mask is stripped from the remaining portions of copperfilm to expose the formed conductive features. In various embodiments,the anti-corrosive layer is a primer layer, and the liquid etch-resistink may be applied to the surface in the form of droplets delivered byan inkjet nozzle, and upon contact with the primer surface, suchdroplets may be soon after (e.g., on the order of micro-seconds)immobilized or “frozen” in place, for example without limitation due toa chemical reaction triggered by the interaction between the etch-resistink and the primer layer, such that further translation or spreading ofthe ink droplet on the primer surface is greatly reduced or stoppedentirely, as described above and in International Publication Nos.WO2016/193978 A2 and WO2016/025949 A1. In various embodiments, theprimer layer and the liquid etch mask ink interact to form abi-component etch mask material.

FIG. 18 shows a block diagram of an apparatus 1800 for producing devicesaccording to embodiments of the disclosure. The apparatus 1800 mayinclude an enclosure 1802. In various exemplary embodiments, theenclosure 1802 may be configured to provide ambient particle filtration,control of relative humidity, control of temperature, or other processcondition controls within a processing environment. The apparatus 1800may include a first substrate transporting mechanism 1804, and asubstrate input unit 1806 configured to receive a substrate from thefirst substrate transporting mechanism 1804. The substrate may comprisean unpatterned device layer, such as substrates 602, 702, 802, or 902and unpatterned device layers 604, 704, 804, or 904 discussed inconnection with FIGS. 6A-9C. A first deposition module 1808 isconfigured to deposit a first layer, such as an anti-corrosive layer629, 729, 829, 929, 1129, 1229, or 1329 discussed in connection withFIGS. 6A-9C and 11-13C, over the unpatterned device layer, wherein firstdeposition module 1808 may comprise a portion that deposits a firstmaterial onto the substrate and portion that further processes thedeposited first material to as to from the anti-corrosive layer, forexample without limitation, by drying, curing, or otherwise processingthe first material. A second deposition module 1812 is configured todeposit an etch mask, such as etch mask 628, 728, 828, or 928 discussedin connection with FIGS. 6A-9D, over the anti-corrosive material layer.The second deposition module 1812 may comprise a portion that deposits asecond material onto the substrate and a portion that further processesthe deposited second material to as to from the etch mask, for examplewithout limitation, by drying, curing, developing, photo-exposing, laserdirect writing, or otherwise processing the second material. Theapparatus 1800 may include a substrate output unit 1820 that providesthe substrate to a second substrate transporting mechanism (not shown).The first substrate transporting mechanism 1804 may transport thesubstrate from a previous processing module or apparatus to theapparatus 1800, and the second substrate transporting mechanism maytransport the substrate to a next processing module or apparatus.

In various exemplary embodiments, the first deposition module 1808 andthe second deposition module 1812 may be configured to deposit materialsby methods such as inkjet printing, spraying, laminating, spin coating,or any other method of deposition, including but not limited to any ofthe deposition methods described above.

In some exemplary embodiments, the apparatus comprises a substratecleaning module 1807 configured to receive the substrate from thesubstrate input unit 1806, clean the substrate, and transfer thesubstrate to the first deposition module 1808. In some exemplaryembodiments, the first deposition module 1808 and the second depositionmodule 1812 may be a single module. In some exemplary embodiments, theapparatus 1800 includes an etching module 1816 configured to etch thematerial in the unpatterned device layer not protected by the etch maskand a stripping module 1818 configured to remove the etchmask from thesubstrate following etching of the material of the unpatterned devicelayer on the substrate.

FIG. 19 shows an exemplary work flow 1900 according to anotherembodiment of the disclosure. At 1902, a primer layer including a firstreactive component is applied onto an unpatterned device layer, such asa metallic surface, e.g., a copper foil. The primer layer may be ananti-corrosive layer such as anti-corrosive layers 629, 729, 829, 929,1129, 1229, or 1329 associated with the embodiments above. At 1904, abi-component etch resist mask is prepared by image-wise printing aliquid etch resist ink comprising a second composition including asecond reactive component onto the primer layer. The bi-componentmaterial resulting from the interaction of the etch resist ink maycomprise, for example, an etch mask such as 628, 728, 828, or 928described in connection with the embodiments above. The secondcomposition may include a second reactive component capable ofundergoing a chemical reaction with the first reactive component. Invarious embodiments, the etch resist ink may be applied to the surfacein the form of droplets delivered by an inkjet nozzle, and upon contactwith the primer surface, such droplets may be soon after (e.g., on theorder of micro-seconds) immobilized or “frozen” in place, for examplewithout limitation due to a chemical reaction triggered by theinteraction between the etch resist ink and the primer layer, such thatfurther translation or spreading of the ink droplet on the primersurface is greatly reduced or stopped entirely, as described above andin International Publication Nos. WO2016/193978 A2 and WO2016/025949 A1.At 1906, unmasked portions of the primer layer (i.e., portions of theprimer layer not covered by the etch mask) are removed before, orduring, an etching process. At 1908, the unmasked portions of themetallic surface are etched to form a patterned device layer, such asthe patterned device layer 630, 730, 830, 930, 1130, 1230, or 1330discussed in connection with the embodiments above. At 1910, the etchresist mask is removed to expose the patterned device layer.

Examples 1-3

The following comparative examples were performed to demonstrate thereduction in undercutting obtained using embodiments of the presentdisclosure as compared to conventional processes not utilizing ananti-corrosive material.

In Examples 2 and 3 detailed below, a polyimine-based agent compositionwas first applied on top of an FR4 copper clad board having a copperthickness of ½ Oz (17 μm) using an Epson stylus 4900 inkjet printer.Then, an etch resist mask was applied on top of the polyimine layer. Anaqueous etch resist composition was prepared using 10% propylene glycolas a humectant and 1% (w/w) 2-Amino-2-methyl propanol as an ionexchange, 0.3% (w/w) of BYK 348 supplied by BYK as a surfactant and 2%(w/w) of Bayscript BA Cyan as a colorant. The etch resist solutionfurther included 24% Joncryl 8085 styrene acrylic resin solution as theanionic etch resist. In the description below, % (w/w) is a measure ofthe concentration of a substance in terms of the percentage by weightrelative to the weight of the composition. The printed samples weredried at 80° C. Copper from the unprotected exposed zones was etchedaway using an etchant bath containing acidic etching solutions. The etchresist mask was stripped off by immersing the etched board in a 1% (w/w)NaOH in aqueous solution at a temperature of 25° C. followed by washingthe FR4 copper board with water and drying it using air at 25° C. InExample 1, another sample was prepared without applying the underlyingagent layer.

Example 1

An etch resist pattern was printed on top of an uncoated copper FR4board at a copper thickness of ½ Oz (17 μm) using an Epson stylus 4900inkjet printer. Reference is made to FIG. 20, which shows a micrographof a cross section of the copper wire sample made according toExample 1. An aqueous etch resist composition was prepared using 10%propylene glycol as a humectant and 1% (w/w) 2-Amino-2-methyl propanolas an ion exchange, 0.3% (w/w) of BYK 348 supplied by BYK as asurfactant and 2% (w/w) of Bayscript BA Cyan as a colorant. The etchresist solution further included 24% Joncryl 8085 styrene acrylic resinsolution as the anionic etch resist reactive component. The drying,etching and removal of the etch resist was conducted as described above.As can be seen from FIG. 20, the slope of the copper sidewalls isrelatively high. Relevant dimensions of the formed conductive featurewere measured and the etch factor was calculated to be 1.5.

Example 2

An etch resist pattern was printed on top of a copper FR4 board coatedwith a polyimine-based coating. A polyimines aqueous solution wasprepared as a mixture of 10% (w/w) LUPASOL G100 (polyethyleneiminehaving molecular weight of 5000) in aqueous solution supplied by BASF,10% (w/w) propylene glycol, 10% n-Propanol and 0.3% (w/w) containingTEGO 500 supplied by Evonik Industries. The poly-imines solution wasapplied using Epson stylus 4900 inkjet printer. The polyimine-basedcoating was left to dry at a room temperature resulting in a fullytransparent uniform coating having a dry thickness of 0.075 μm coveringthe entire surface of the board without crystal formation. The etchresist composition was printed on the coated copper board using theprocess and materials as detailed above. Relevant dimensions of theformed conductive feature were measured and the etch factor wascalculated to be 2.5.

Example 3

An etch resist pattern was printed on top of a copper FR4 board coatedwith a polyimine-based coating. Reference is made to FIG. 21, whichshows a micrograph of a cross section of a copper wire the copper wiresample made according to Example 3, according to embodiments of thedisclosure. A polyimine-based coating was coated on top of FR4 boardusing Epson stylus 4900 inkjet printer. The polyimine solution wasprepared as a mixture of an aqueous solution of 10% (w/w) LUPASOL HF(polyethyleneimine having a molecular weight of 25,000) supplied byBASF, 10% (w/w) propylene glycol, 10% n-Propanol and 0.3% (w/w)containing TEGO 500 supplied by Evonik Industries. The coated plate wasleft to dry at room temperature resulting in a fully transparent uniformcoating having a thickness of 0.075 μm dry layer covering the entiresurface without crystal formation.

An etch resist composition was prepared as detailed in Example 1. Theetching of the unmasked copper and the removal of the etch resist maskwere conducted as described with respect to Example 1. As shown in FIG.21, the slope of the sidewalls of the copper wire is much smaller thanthe sample prepared without the undercut eliminating layer as shown inFIG. 20. Relevant dimensions of the formed conductive feature weremeasured and the etch factor was measured and found to be 7.5.

Table 1 below summarizes some characteristics of the results of thethree Examples.

TABLE 1 undercut prevention W2- Height- Etch Example Agent MW W1 X HFactor 1 None — 20 10 15 1.5 2 Lupasol G100 5000 12 6 15 2.5 3 LupasolHF 25,000 4 2 15 7.5

The following comparative examples were performed to demonstrate theimprovement in formation of an etch mask using a primer layer and aninkjet printed etch resist ink, wherein upon contact with the primerlayer, one or more reactions occur between components of the primerlayer and the etch resist ink so that a bi-component etch mask materialis formed and droplets of the etch resist ink are rapidly (e.g., on theorder of micro-seconds) immobilized or frozen and subsequent spreadingand/or translation of such droplets is greatly reduced.

Examples 4-12

Using an Epson stylus 4900 inkjet printer exemplary etch resistcompositions (second composition as described in here) were printed onan FR4 copper clad boards having a thickness of ½ Oz, ⅓ Oz and 1 Oz. Insome cases, the copper was first coated using an Epson stylus 4900inkjet printer with a fixating composition (first composition asdescribed in here) forming a fixating layer on which the etch resistcompositions were selectively printed according to a predeterminedpattern. In the description below, % (w/w) is a measure of theconcentration of a substance in terms of the percentage by weightrelative to the weight of the composition. Copper from the unprotectedby the etch resist—exposed zones was etched away using an etchant bathcontaining a ferric chloride etchant solution of strength 42° Baumesupplied by Amza [pernix 166]. The etching was performed in a SprayDeveloper S31, supplied by Walter Lemmen GMBH, at a temperature of 35°C. for 3 minutes. The etch resist mask was stripped off by immersing theetched board in a 1% (w/w) NaOH in aqueous solution at a temperature of25° C. followed by washing the FR4 copper board with water and drying byair at 25° C. The copper boards were also etched, in some experiments,using an industrial etching unit including hyper and super etchingunits, manufacture by Universal or Shmidth containing Copper chloridesolution for etching non-protected copper.

Example 4

An etch resist composition printed on top of an uncoated copper FR4board (comparative data). An etch resist composition (secondcomposition) was prepared with 10% propylene glycol and 1% (w/w)2-Amino-2-methyl propanol, 0.3% (w/w) of BYK 348 supplied by BYK and 2%(w/w) of Bayscript BA Cyan. These materials were dissolved in watercontaining 24% Joncryl 8085 styrene acrylic resin solution as theanionic reactive component. Using an Epson stylus 4900 inkjet printerthe etch resist composition was printed on an FR4 copper clad boardhaving a thickness of ½ Oz to produce the etch resist mask. The dry etchresist thickness was 5 microns.

The etch mask was visually inspected, and the printed patterndemonstrated a very poor print quality with extremely poor edgedefinition, line breaks and severe shorts between the lines.

Example 5

The etch resist composition was prepared as detailed in Example 4. Aprimer or fixating composition was prepared as a mixture of an aqueoussolution of 10% (w/w) LUPASOL PR8515 supplied by BASF (Polyethylenimineas the cationic reactive component), 10% (w/w) Propylene glycol, 10%n-Propanol and 0.3% (w/w) containing TEGO 500 supplied by EvonikIndustries (a foam-inhibiting substrate wetting additive).

An FR4 Copper board was coated using Epson stylus 4900 inkjet printer.The coated plate was left to dry at room temperature resulting in afully transparent uniform coating having a thickness of 0.3n dry layercovering the entire surface without any crystal formation. Using anEpson stylus 4900 inkjet printer, the etch resist composition wasprinted on the coated copper board and dried at 80° C. to produce abi-component etch resist mask. The etch mask was visually inspected toshow a better print quality than Example 4 but still a relatively poorprint quality with broadens lines and shorts between lines. The etchingof the unmasked copper and removal of the etch resist mask wereconducted as detailed in example 4. The wiring pattern produced afterthe etching process had an identical image as the etch resist mask withthe same broaden lines and shorts between lines. It should be noted thatfor certain applications the print quality as exhibited by Example 5 maybe sufficient.

Example 6

The etch resist composition was prepared as detailed in Example 4. Thefixating composition was prepared as detailed in Example 5 with theexception of replacing 0.3% (w/w) TEGO 500 with 0.3% (w/w) TEGO 500containing 13% (w/w) concentrate HCl.

An FR4 Copper board was coated with the fixation composition using Epsonstylus 4900 inkjet printer as detailed in Example 5 and after drying acoating layer as detailed in Example 5 was formed. Similarly to Example5, the etch resist composition was inkjet-printed on the coated copperboard and dried at 80° C. to produce a bi-component etch resist mask.The etch resist pattern demonstrated a high print quality withwell-defined thin lines having a thickness of down to 2 millimeters,sharp edges and no line breaks. The etching of the unmasked copper andremoval of the etch resist mask were conducted as detailed in example 4.The wiring pattern produced by the etching and stripping processesdemonstrated a well-defined pattern with thin lines having a width ofdown to 15 microns sharp edges and no line breaks.

Example 7

Bi-component reaction, an etch resist composition printed on a coppersurface coated with a reactive cationic composition containingHydrochloric acid (HCl). The etch resist composition was prepared asdetailed in Example 4. A fixating composition was prepared as a mixtureof an aqueous solution of 10% (w/w) Styleze W-

20 (supplied by ISP as a 20% polymer in aqueous solution), 0.1% of BYK348, and 13% (w/w) concentrate HCl.

An F4F copper board was covered using a Mayer rod with the fixatingcomposition to produce a dry layer having a thickness of 0.4n. Thecoated board was left to dry, resulting in a fully transparent coatingover the entire copper surface with no crystal formation. Similarly toExample 5, the etch resist composition was inkjet-printed on the coatedcopper board and dried at 80° C. to produce a bi-component etch resistmask.

The etch resist pattern demonstrated a high print quality withwell-defined and thin lines down to 2 millimeters with sharp edges andno line breaks. Residue of the fixating layer that was not covered bythe etch resist composition was washed by socking the board in water for2 minutes at temperature of 25° C. and dried at 80° C. Etching of theexposed copper and removal of the etch resist mask were conducted asdetailed in Example 4. The wiring pattern on the board demonstratedwell-defined thin lines with a width down to 2 mil containing sharpedges and no line breaks.

Example 8

Bi-component reaction, an etch resist composition printed on a coppersurface coated with a reactive cationic composition containingHydrochloric acid (HCl). The etch resist composition was prepared asdetailed in Example 4. A fixating composition was prepared as a mixtureof an aqueous solution of 10% (w/w) Lupasol HF (supplied by BASF as a56% polymer in aqueous solution), 0.1% of BYK 348 containing 13% (w/w)concentrate HCl.

An FR4 copper board was covered using a Mayer rod with the fixatingcomposition to produce a dry layer having a thickness of 1μ. The coatedboard was left to dry, resulting in a fully transparent coating over theentire copper surface with no crystal formation. Similarly to Example 5,the etch resist composition was inkjet-printed on the coated copperboard and dried at 80° C. to produce a bi-component etch resist mask.

The etch resist pattern demonstrated a high print quality withwell-defined and thin lines down to 2 mil contained sharp edges and noline breaks. Residue of the fixating layer not covered by the etchresist composition was washed by socking the board in water for 3minutes at temperature of 25° C. and dried at 80° C. Etching of theexposed copper and removal of the etch resist mask were conducted asdetailed in Example 4. The wiring pattern on the board demonstratedwell-defined thin lines with a width down to 2 mil containing sharpedges and no line breaks.

Example 9

Bi-component reaction: an etch resist composition printed on a coppersurface coated with a reactive cationic composition containingHydrochloric acid (HCl). The etch resist composition was prepared asdetailed in Example 5. A fixating composition was prepared as a mixtureof an aqueous solution of 10% (w/w) Lupasol PN 50 (supplied by BASF as a49% polymer in aqueous solution), 0.1% of BYK 348 containing 13% (w/w)concentrated HCl.

An FR4 copper board was covered using a Mayer rod with the fixatingcomposition to produce a dry layer having a thickness of 1μ. The coatedboard was left to dry, resulting in a fully transparent coating over theentire copper surface with no crystal formation. Similarly to Example 5,the etch resist composition was inkjet-printed on the coated copperboard and dried at 80° C. to produce a bi-component etch resist mask.

The etch resist pattern demonstrated a high print quality withwell-defined and thin lines down to 2 millimeters containing sharp edgesand no line breaks. Residue of the fixating layer was washed as detailedin Example 8. Etching of the exposed copper and removal of the etchresist mask were conducted as detailed in Example 1. The wiring patternon the board demonstrated well-defined thin lines with a width down to 2mil containing sharp edges and no line breaks.

Example 10

Bi-component reaction, an etch resist composition printed on a coppersurface coated with a reactive composition containing citric acid. Theetch resist composition was prepared as detailed in Example 4. Afixating composition was prepared as a mixture of an aqueous solution of10% (w/w) citric acid, 25% (w/w) Propylene glycol, containing 0.3% (w/w)TEGO 500 supplied by Evonik Industries (a foam inhibiting substratewetting additive).

An FR4 Copper board was coated with the fixating composition using anEpson stylus 4900 inkjet printer. The coated plate was left to dry atroom temperature resulting in a fully transparent uniform coating havinga thickness of 0.3p, dry layer covering the entire surface withoutcrystal formation. Similarly to Example 5, the etch resist compositionwas inkjet-printed on the coated copper board and dried at 80° C. toproduce a bi-component etch resist mask.

The etch resist pattern demonstrated a high print quality withwell-defined and thin lines down to 2 mil containing sharp edges and noline breaks. Etching of the exposed copper and removal of the etchresist mask were conducted as detailed in Example 4. The wiring patternon the board demonstrated well-defined thin lines with a width down to 2mil containing sharp edges and no line breaks.

Example 11

Bi-component reaction, coating composition containing the etch resistcomposition was prepared as detailed in Example 4. A fixatingcomposition was prepared as a mixture of an aqueous solution of 2.5%(w/w) Zn(NO₃)2, 3.75% (w/w) Calcium acetate, 0.2% (w/w) Capstone 51, 5%(w/w) n-Propanol and 5% (w/w) Lupasol FG (supplied by BASF).

An FR4 copper board was covered using a Mayer rod with the fixatingcomposition to produce a dry layer having a thickness of 0.5μ. Thecoated board was left to dry, resulting in a fully transparent coatingover the entire copper surface with no crystal formation. Similarly toExample 5, the etch resist composition was inkjet-printed on the coatedcopper board and dried at 80° C. to produce a bi-component etch resistmask.

Similarly to Example 5, the etch resist composition was inkjet-printedon the coated copper board and dried at 80° C. to produce a bi-componentetch resist mask.

The etch resist pattern demonstrated a high print quality withwell-defined and thin lines down to 2 mil containing sharp edges and noline breaks. Etching of the exposed copper and removal of the etchresist mask were conducted as detailed in Example 4. The wiring patternon the board demonstrated well-defined thin lines with a width down to 2mil containing sharp edges and no line breaks.

Example 12

A etch-resist composition was prepared as a mixture of an aqueoussolution of 8% (w/w) PVA, 24% Joncryl 8085 styrene acrylic resinsolution (supplied as a 42% polymer in aqueous solution) and 1.5% of2-Amino 2-methyl propanol.

A fixating composition was prepared as follows: 2% (w/w) of Basacid Red495, 10% (w/w) Propylene glycol, 10% n-Propanol, 0.3% (w/w) TEG0500, 10%(w/w) Lupasol G20 (supplied by BASF) containing 12% (w/w) HClconcentrated. An FR4 copper board was covered using a Mayer rod with theetch-resist composition to produce a dry layer having a thickness of 2.4The coated board was left to dry, resulting in a fully transparentcoating over the entire copper surface with no crystal formation. Thefixating composition was inkjet-printed on the coated copper board anddried at 80° C. to produce a bi-component etch resist mask.

Similarly to Example 5, the etch resist composition was inkjet-printedon the coated copper board and dried at 80° C. to produce a bi-componentetch resist mask.

The etch resist pattern demonstrated a high print quality withwell-defined and thin lines down to 2 mil containing sharp edges and noline breaks. Residue of the coating which was not coved by the etchresist ink was washed by socking the board in aqueous solution of 1%(w/w) NaHCO₃ for 30 seconds at temperature of 25° C. and dried at 80° C.Etching of the exposed copper and removal of the etch resist mask wereconducted as detailed in Example 4. The wiring pattern on the boarddemonstrated well-defined thin lines with a width down to 2 milcontaining sharp edges and no line breaks.

Cationic Compositions (Fixating Reactive Component)

Non-limiting examples of cationic reactive component (a fixatingreactive component) may include polyamides, for example,Polyethyleneimine, divalent metal salts, acids both organic orinorganic, Heteropolymer of vinyl pyrolidon, dimethylaminopropylmethacrylamide; methacryloylaminopropy lauryl dimethyl ammoniumchloride, Poly-quaternary amines and polyamines in natural form or asammonium salts.

The thickness of a dried fixating layer may be as thin as around 0.01microns. A typical desired thickness for a dry layer may vary between0.025 and 5 microns.

The cationic composition (first composition) may include additionalcomponents adapted to suit the method of application and the desiredwidth of the dried layer. The composition may have a viscosity suitablefor spraying or ink-jet printing, for example, a viscosity of less than60 centipoise or between 3-20 cP (centipoise) at an ambient temperature,respectively. The composition might have higher viscosity in case adifferent coating method is applied.

In some embodiments, an acidic solution may be added to the firstsolution in order to increase reactivity of first layer to the copperlayer 320 as well as its reactivity to the etch resist or fixatinglayer. In some embodiments, the first layer may further be developed,for example, by water, prior to the copper etch process. In someembodiments, the applied first layer may be dried prior to theapplication of the second layer. The as-dried layer may contain mainlythe first reactive material. The first layer may be dried using anyknown drying method.

Some non-limiting examples of first reactive components (e.g., afixating component) and first compositions (e.g., fixating composition,cationic composition) are listed in Table 1.

TABLE 1 Reactive component Fixating Composition chemical group 1 Aqueoussolution of 10% (w/w) Polyethyleneimine, Polyethyleneimine, 10% 10%(w/w) Propylene glycol, 10% n-Propanol, 0.3% (w/w) Molecular weight(w/w) containing surfactants (Mw) 500-5000 2 Aqueous solution of 10%(w/w) Polyethyleneimine Polyethyleneimine, 10% Propylene glycol, 10%n-Propanol, (w/w) Mw 6000-2000000 0.3% (w/w) containing surfactants 3Aqueous solution of 10% (w/w) Heteropolymer of Heteropolymer of VP, 10%(w/w) Propylene glycol, 10% n-Propanol, vinylpyrolydon, 0.3% (w/w)containing surfactants dimethylaminopropyl methacrylamide &methacryloylaminopropy lauryl dimethyl ammonium chloride 4 Aqueoussolution of 10% (w/w) Poly-quaternary Poly-quaternary amines amine, 10%(w/w) Propylene glycol, 10% n- Propanol, 0.3% (w/w) containingsurfactants 5 Aqueous solution of 3% (w/w) Polyethyleneimine,Polyethyleneimine 5% metal salts, 10% (w/w) Propylene glycol, 10% n- (Mw500-5000) contains Propanol, 0.3% (w/w) containing surfactants divalentmetal salts (e.g., Ca, Zn, Mg, etc.) 6 Aqueous solution of 3% (w/w)Polyethyleneimine, Polyethyleneimine (Mw 5% metal salts, 10% (w/w)Propylene glycol, 10% n- 600-2000000 contains Propanol, 0.3% (w/w)containing surfactants divalent metal salts (Ca, Zn, Mg, etc.)

Anionic Compositions (Etch Resist Polymeric Component)

In some embodiments, the second reactive component (e.g., a polymericcomponent) may be an etch-resistant component (resistant to the metallicetching solution). The second reactive component may include polyanionactive groups such as: acrylates, styrene acrylates; phosphates andsulfonates. A droplet of the etch-resist ink applied on top of the first(e.g., fixating) layer can be immobilized and fixated to the coppersurface due to a chemical reaction between the first reactive material(that includes poly-cations) and the second reactive material (thatincludes poly-anions). Since the fixation is very rapid (in themicro-second range) the dimension of the printed pattern is similar tothe dimension of the required pattern. The compound formed by thereaction of first reactive material and the second reactive material(both of which are soluble in water) should be insoluble in copper etchsolution.

The second composition may have a viscosity suitable for inkjet printingof less than 60 cP, for example, 3-20 cP at the jetting temperature. Thecomposition might have higher viscosity in case a different coatingmethod is applied. In some embodiments, the second composition mayinclude no more than 20% (w/w) of the reactive component to sustain therequired viscosity. In some embodiments, the polyanion reactivecomponent (the etch-resist polymer) when dissolved in composition mayhave a maximal of 5000 molar weight (e.g., the polymer may haverelatively short chains). In some embodiments, the etch-resist polymermay have higher molar weight resulting in a composition in a form ofpolymeric emulsion or dispersion. The second reactive component may havehigh acidic value, for example, having more than 100 reactive anionicgroups per gram of polymer. For example, an etch-resist polymeraccording to embodiments of the invention may have more than 200, 240,300 or more reactive anionic groups in each chain.

Some non-limiting examples of the second reactive components (etchresistant components) and second compositions (etching resistantcompositions, anionic compositions) are listed in Table 2.

TABLE 2 No. etching resistant composition Second reactive component 1 2%(w/w) of Cyan dye, 10% acrylates propylene glycol, 1% (w/w) 2- Mw800-17,000 Amino-2-methyl propanol and Acid No 130-240 0.3% (w/w) ofsurfactant were in Solution or emulsion dissolved in water containing24% styrene acrylic resin solution. 2 2% (w/w) of Cyan dye, 10%Organo-phosphates propylene glycol, 1% (w/w) 2- Mw 800-17,000 AcidAmino-2-methyl propanol and No 130-240 0.3% (w/w) of surfactant were InSolution or Emulsion dissolved in water containing 24% phosphates resinsolution. 3 2% (w/w) of Cyan dye, 10% Organo-Sulfonates propyleneglycol, 1% (w/w) 2- Mw 800-17,000 Amino-2-methyl propanol and Acid No130-240 0.3% (w/w) of surfactant were In Solution or emulsion dissolvedin water containing 24% sulfonates resin solution.

This description and the accompanying drawings that illustrate exemplaryembodiments should not be taken as limiting. Various mechanical,compositional, structural, and operational changes may be made withoutdeparting from the scope of this description and the claims, includingequivalents. In some instances, well-known structures and techniqueshave not been shown or described in detail so as not to obscure thedisclosure. Like numbers in two or more figures represent the same orsimilar elements. Furthermore, elements and their associated featuresthat are described in detail with reference to one embodiment may,whenever practical, be included in other embodiments in which they arenot specifically shown or described. For example, if an element isdescribed in detail with reference to one embodiment and is notdescribed with reference to a second embodiment, the element maynevertheless be claimed as included in the second embodiment.

For the purposes of this specification and appended claims, unlessotherwise indicated, all numbers expressing quantities, percentages, orproportions, and other numerical values used in the specification andclaims, are to be understood as being modified in all instances by theterm “about,” to the extent they are not already so modified.Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that may vary depending upon the desired propertiessought to be obtained. At the very least, and not as an attempt to limitthe application of the doctrine of equivalents to the scope of theclaims, each numerical parameter should at least be construed in lightof the number of reported significant digits and by applying ordinaryrounding techniques.

It is noted that, as used in this specification and the appended claims,the singular forms “a,” “an,” and “the,” and any singular use of anyword, include plural referents unless expressly and unequivocallylimited to one referent. As used herein, the term “include” and itsgrammatical variants are intended to be non-limiting, such thatrecitation of items in a list is not to the exclusion of other likeitems that can be substituted or added to the listed items.

Further, this description's terminology is not intended to limit thedisclosure. For example, spatially relative terms—such as “beneath”,“below”, “lower”, “above”, “upper”, “proximate”, and the like—may beused to describe one element's or feature's relationship to anotherelement or feature as illustrated in the figures. These spatiallyrelative terms are intended to encompass different positions (i.e.,locations) and orientations (i.e., rotational placements) of a device inuse or operation in addition to the position and orientation shown inthe figures. For example, if a device in the figures is turned over,elements described as “below” or “beneath” other elements or featureswould then be “above” or “over” the other elements or features. Thus,the exemplary term “below” can encompass both positions and orientationsof above and below. A device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

Further modifications and alternative embodiments will be apparent tothose of ordinary skill in the art in view of the disclosure herein. Forexample, the devices and methods may include additional components orsteps that were omitted from the diagrams and description for clarity ofoperation. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the present teachings. It isto be understood that the various embodiments shown and described hereinare to be taken as exemplary. Elements and materials, and arrangementsof those elements and materials, may be substituted for thoseillustrated and described herein, parts and steps in workflows andprocesses may be in alternate order, and certain features of the presentteachings may be utilized independently, all as would be apparent to oneskilled in the art after having the benefit of the description herein.Changes may be made in the elements described herein without departingfrom the spirit and scope of the present teachings and following claims.

Although various exemplary embodiments herein describe manufacture of aPCB, those having ordinary skill in the art would appreciate that otherelectrical and optical devices or components that are made using similaretching and metal or conductive line patterning techniques areencompassed within the scope of the disclosure and claims, and PCBs arediscussed as one non-limiting, exemplary application. Other devices andcomponents that may be manufactured according to exemplary embodimentsherein include, but are not limited to, microchips, electronic displays,microchips, solar cells, and other electronic, optical, or other devicesand components.

It is to be understood that the particular examples and embodiments setforth herein are non-limiting, and modifications to structure,dimensions, materials, and methodologies may be made without departingfrom the scope of the present teachings. Other embodiments in accordancewith the present disclosure will be apparent to those skilled in the artfrom consideration of the specification and practice of the presentdisclosure. It is intended that the specification and examples beconsidered as exemplary only, with the following claims being entitledto their fullest breadth, including equivalents, under the applicablelaw.

What is claimed is:
 1. A method of making a device patterned with one ormore electrically conductive features, the method comprising: depositinga conductive material layer over an electrically insulating surface of asubstrate; depositing an anti-corrosive material layer over theconductive material layer; depositing an etch-resist material layer overthe anti-corrosive material layer, the etch-resist material layer andthe anti-corrosive material layer forming a bi-component etch mask in apattern resulting in covered portions of the conductive material layerand exposed portions of the conductive material layer, the coveredportions being positioned at locations corresponding to one or moreconductive features of the device; performing a wet-etch process toremove the exposed portions of the conductive material layer from theelectrically insulating substrate; and removing the bi-component etchmask to expose the remaining conductive material of the covered portionsof the conductive material layer, thereby forming the one or moreelectrically conductive features of the device.
 2. The method of claim1, wherein depositing the anti-corrosive material layer over theconductive material layer comprises depositing a polymer over theconductive material layer.
 3. The method of claim 1, wherein depositingthe anti-corrosive material layer over the conductive material layercomprises depositing an organic material over the conductive materiallayer.
 4. The method of claim 3, wherein the organic material comprisesone or more -imine groups.
 5. The method of claim 3, wherein the organicmaterial comprises one or more -amine groups.
 6. The method of claim 3,wherein the organic material comprises one or more -azole groups.
 7. Themethod of claim 3, wherein the organic material comprises one or more-hyrazine groups.
 8. The method of claim 3, wherein the organic materialcomprises an amino acid.
 9. The method of claim 3, wherein the organicmaterial comprises a Schiff Base.
 10. The method of claim 1, furthercomprising, during performing of the wet-etching process, dissociating aportion of anti-corrosive material from the bi-component etch mask andadsorbing the dissociated portion of anti-corrosive material to an outersurface of the conductive material layer under the bi-component etchmask.
 11. The method of claim 1, further comprising, during performingof the wet-etching process, protecting a portion of the conductivematerial layer proximate the bi-component etch mask from being removedduring removal of a portion of the conductive material layer proximatethe electrically insulating surface of the substrate.
 12. The method ofclaim 1, wherein depositing the anti-corrosive material layer over theconductive material layer comprises depositing the anti-corrosivematerial layer in a blanket coating over the conductive material layer.13. The method of claim 1, wherein depositing the anti-corrosivematerial layer over the conductive material layer comprises depositingthe anti-corrosive material layer in the pattern corresponding to theone or more conductive features.
 14. The method of claim 1, whereindepositing the etch-resist material layer comprises depositing theetch-resist material layer in a blanket coating over the anti-corrosivematerial layer.
 15. The method of claim 1, wherein depositing theetch-resist material layer comprises depositing the etch-resist materiallayer using at least one of inkjet printing, slot die coating, spincoating, or lamination.
 16. The method of claim 1, wherein depositingthe anti-corrosive material layer comprises depositing theanti-corrosive material layer using at least one of inkjet printing,slot die coating, spin coating, or lamination.
 17. The method of claim1, wherein a thickness of the anti-corrosive material layer ranges from5 μm to 40 μm.
 18. An apparatus for making a device patterned withelectrically conductive features, the apparatus comprising: a firstdeposition module configured to deposit an anti-corrosive material layerover a conductive material layer over an electrically insulating surfaceof a substrate; a second deposition module configured to deposit anetch-resist material layer over the anti-corrosive material layer; and awet etching module configured to etch the conductive material layer ofthe substrate.
 19. The apparatus of claim 18, further comprising a firstprocessing module configured to cure the anti-corrosive material layer.20. The apparatus of claim 18, further comprising a second processingmodule configured to cure the etch-resist material layer to form abi-component etch mask.
 21. The apparatus of claim 18, wherein the firstdeposition module comprises a first inkjet printing module.
 22. Theapparatus of claim 18, wherein the second deposition module comprises asecond inkjet printing module.
 23. The apparatus of claim 18, furthercomprising an enclosure configured to provide processing conditioncontrol, the enclosure housing the first deposition module and thesecond deposition module.
 24. The apparatus of claim 18, furthercomprising a stripping module configured to remove the bi-component etchmask from the conductive material layer.
 25. A device patterned withelectrically conductive features, comprising: a substrate having anelectrically insulating surface; and a conductive feature disposed onthe electrically insulating surface, the conductive feature comprising;a height measured in a direction normal to the electrically insulatingsurface; a first width measured at the electrically insulating surface;and a second width measured at an end of the conductive feature oppositethe electrically insulating surface along the height of the conductivefeature; wherein a value of half a difference between the first widthand the second width divided by the height is at least
 2. 26. The deviceof claim 25, wherein the value of half the difference between the firstwidth and the second width divided by the height is at least
 5. 27. Thedevice of claim 25, wherein the height of the conductive feature is 15μm and the difference between the first width and the second width isless than 6 μm.